What follows is the new version of the Books section for the Goosebumps HorrorLand page, which I added to said page after getting all the bugs worked out of it, replacing the original "prose" version. Unfortunately, someone eventually saw fit to remove this version and replace it with a blander, "basic" version, as well as removing the future books and most of the sources. While I have spoken with this person and eventually agreed with their reasonings, I have chosen to preserve the original version here, covering the first twenty books.
Plot: 12-year-old Britney Crosby and her friend Molly Molloy are faced with a visit from Britney's bratty cousin Ethan, who's into ventriloquism and brings along his dummy, Mr. Badboy. Unfortunately for Britney, Mr. Badboy turns out to be none other than the evil Slappy, who is up to his usual tricks. Shortly after they defeat him, Britney and Molly are invited to the terrifying theme park known as HorrorLand, where they soon find that all is not as it seems.
Fear File: Ad for info on HorrorLand, Stagger Inn Doom Service Menu, and Map #1 (Last Ride Cab Company, Stagger Inn, Find the Eyeball, Madame Doom).
Escape HorrorLand chapter: Stagger Inn
Notes: Early print runs mistakenly had the Classic Token text as "Find this token online", the same as the HorrorLand Token text.
Plot: Billy Deep and his sister Sheena always expect adventure when they visit their uncle Dr. D. This time around, they are faced with the legend of the fearsome pirate captain Long Ben One-Leg... who turns out to not be as dead as believed! Later, an invitation to HorrorLand leads the siblings and their new friend Matt into another terrifying situation.
Fear File: Two Madame Doom Cards (one blank, one with the numbers 394)23 that read "ESCAPE" if put up to a mirror), Black Lagoon Water Park Rules and Regulations, and Map #2 (Black Lagoon Water Park with Loch Ness Lake, Bottomless Canoe Ride, Quicksand Beach, The Swim-with-a-Hungry-Shark Ride, The Alligator Swimming Pond).
Escape HorrorLand chapter: Black Lagoon Water Park
Notes: This book ignores the events of Deep Trouble II, which also took place one year after Deep Trouble.
Plot: Athletic Matt Daniels and his sister Livvy can't stand their neighbor Bradley "Worm" Wormser, who copies Matt in every way he can. When Bradley orders a can of Monster Blood on Matt's computer, Matt decides to use the Blood in a prank on him, but it backfires in a big way. Even after solving that problem, Matt is faced with another: an invitation to HorrorLand, where he makes new friends and discovers an old enemy may be lurking around!
Fear File: Postcard: "HorrorLand is not what it used to be", Monster Police Flyer, Map #3 (Monster Police Headquarters, Crocodile Café, Dr.Twisted's Science Lab, The Hungry Crocs Piggyback Ride).
Escape HorrorLand chapter: Monster Police
Notes: Early promotional material suggested that Livvy would accompany Matt to HorrorLand. However, this was not the case in the published book.
Plot: One year ago, Carly Beth Caldwell looked into the face of fear... her own! And the mask that she thought she was done with won't stop haunting her. But when she and her friend Sabrina Mason visit the abandoned stable at Tumbledown Farms, they find that the mask has a deeper history than suspected. The only way for Carly Beth to put the past behind her is to discover the stable's strange secret, even if that means putting the mask on one more time. And even then, the nightmare is about to get worse, as an invitation to HorrorLand leads to Carly Beth and Sabrina making new friends, as well as a shocking discovery about the intentions of their hosts.
Fear File: A video showing Slappy in HorrorLand, Haunted Theater Flyer, Map #4 (Zombie Plaza, including the Haunted Theater, the Make-A-Face mask shop, the "It's A Howl" pet shop and the "Worm and Bait" shop).
Escape HorrorLand chapter: Zombie Plaza
Notes: Early promotional materials suggested a different plotline, in which Carly Beth, Sabrina and their friends Steve and Chuck would have to spend a night in an entire house full of haunted masks, and that all four would go to HorrorLand.
This book ignores the events of The Haunted Mask II, which also took place one year after The Haunted Mask.
Plot: Robby Schwartz creates comic strips on his computer, starring bizarre supervillains. His favorite is the menacing Dr. Maniac, a madman in every sense of the word. But soon, fantasy and reality collide when Dr. Maniac appears in Robby's hometown in order to carry out his latest dastardly plan. And the action doesn't stop after creator defeats creation, as an invitation to HorrorLand arrives. Old foes and new friends are waiting there for Robby... as is a hair-raising encounter with the werewolves of Werewolf Village!
Fear File: A message from Lizzy to Luke, a composition book with the words "One Day at HorrorLand" on the cover, and Map #5 (Werewolf Village, including the Werewolf Petting Zoo, Wolfsbane Forest, a cemetary and Dr. Maniac's World of Pain).
Escape HorrorLand chapter: Werewolf Village
Notes: In early promotional material, Robby's older brother Sam was the creator of Dr. Maniac, and became trapped in one of his own comic strips, which continued updating after he vanished. In the book, Robby is Sam's older brother, as well as the creator of Dr. Maniac. They also have a sister named Taylor.
Plot: Abby Martin and her little brother Peter are staying with their Egyptologist Uncle Jonathan. But their room looks more like a tomb! And what's with all the strange moaning in the night? Later, Abby visits HorrorLand, where she meets another Very Special Guest, Michael "Monster" Munroe, and the Horror named Byron. But can he really help them out?
Fear File: Egyptian Message reading "Panic Park", 4 of the Ten top scariest rides in HorrorLand and Map #6 (with the A-Nile-Ator Roller Coaster, a sphinx, and the Terror Tombs).
Escape HorrorLand chapter: Rides and Entertainment
Notes: Early promotional materials indicated that Abby's brother, Peter would accompany her in HorrorLand, but this was not the case in the published novel.
Plot: Michael "Monster" Munroe has had it with his teacher Mrs. Hardesty. But during an attempt to get even, he discovers her true nature... and a giant egg in her attic! Later, Michael visits HorrorLand and meets Abby Martin, another of the Very Special Guests. With his help, the VSGs finally manage to access the internet from the underground tunnels. It is here that they discover a blog by two previous visitors to HorrorLand, as well as information about the founders of HorrorLand and the mysterious Panic Park, which could be the only safe way out of their predicament... or is it?
Fear File: Posters for The Wheel of Fire and The Mirror Mansion (in Panic Park), a job application for a HorrorLand Horror, and Map #7 (featuring the entrance to HorrorLand, the Bat Barn and the Underground Horrors' HQ).
Escape HorrorLand chapter: Monster Resources
Notes: Early promotional materials indicated this book would feature an "evil curse" which was not present in the published story.
The founder of HorrorLand is Kit Katzman. The founder of Panic Park is Karloff Mennis.
Plot: A picture is worth a thousand screams... especially one taken by Julie's new camera, which has the bizarre power to predict a nasty future for anyone in its way. If that's not scary enough, a trip to HorrorLand is also in Julie's future, including a nightmarish experience in the Tunnel of Screams!
Fear File: Two Word puzzles with the Horrorland stamp that comes alive, Memo to the All Crude Cart Staff, Map #8 (The Tunnel of Screams and the Play Pen).
Escape HorrorLand chapter: Park Upkeep and Improvements
Notes: Julie's last name was not revealed until Escape From HorrorLand.
Plot: Spooky legends aside, animal-loving siblings Boone and Heather Dixon can't wait to get to Camp Hither, but an infestation of snakes soon changes their minds. Even after they can get to the bottom of the trouble, more danger awaits when Boone gets to HorrorLand and finds a group of kids being strangled by what appears to be purple snakes!
Fear File: A receipt from the store "Dead, Bats & Beyond: Supervillain Outfitters", Dr. Maniac's To Do List, A Memo to Stagger Inn, Map #9 (The Guillotine Museum and the Monster Obstacle Course)
Escape HorrorLand chapter: V.I.V.s: Very Important Villains
Notes: Notes in the reissue for Night of the Living Dummy suggested that a villain named Mr. Slither would appear. However, it appears that name was changed before this book's release.
Early promotional material suggested that Heather would accompany her brother to HorrorLand. However, this is not the case in the published book.
Plot synopses for the audiobook edition name the protagonists as Joel and Zoey rather than Boone and Heather, and refer to the camp as "Camp Slither" rather than "Camp Hither."
When the Very Special Guests discover the room with the villains' images, Captain Ben is mistakenly named as Captain Jack.
Plot: Twins Jillian Gerard and Jackson Gerard need help. They've developed some really strange abilities, and soon find themselves being targeted by an evil organization that wants to control that power. And the danger doesn't stop once they get to HorrorLand, where they join the rest of the Very Special Guests and meet a couple of surprising faces from the past.
Fear File: A coded message for Lizzy and Luke, a page from a top secret document, and Map # 10 (Goodbye Land, with The Doom Slide, The Pretzel Pal and The R.I.P.P.E.R. Dipper.)
Escape HorrorLand chapter: The Power of 10
Notes: It was originally stated that this book would take place entirely in HorrorLand, but this was changed by the time the book itself came out.
The Morris siblings finally appear at the very end of the book.
Plot: Luke and Lizzy Morris have returned to HorrorLand, intending to save the Very Special Guests from their mysterious enemy. But even their best efforts can't stop the VSGs from fleeing to Panic Park, where the sixteen must confront some old foes from their pasts, and finally meet the man known as The Menace, the person who lured them into Panic Park and expects them to stay there... forever!
Fear File: Business card for Inspector Cranium, FAQ about the Vampire State Building, Map # 11 (Vampire Village, including the Vampire State Building, Vulture Beach and the Coffin Cruise).
Escape HorrorLand chapter: Not yet revealed.
Notes: Early promotional materials identified this book as Streets of Panic Park. However, that title was eventually given to the following book during production.
Plot: They escaped from HorrorLand. But they ended up trapped in Panic Park instead, at the mercy of The Menace. In order to escape the nightmare for good, fourteen Very Special Guests and two returning visitors to HorrorLand must face their fear with the help of some frightful allies... and finally bring the adventure to an end.
Fear File: Note with pictures of two tokens, survey from the Stagger Inn staff and Map #12, including the Spider House, the Free-Fall Bungie Jump, and a Frozen Eyeballs stand.
Escape HorrorLand chapter: Not yet available.
Notes: Early promotional materials identified this book as The Last Horror. However, that title was eventually changed.
Many truths are revealed, including the true identity of the villains, the nature of Panic Park, and the real identity of Monster X.
Special - Welcome to HorrorLand: A Survival Guide
Plot: Luke and Lizzy have done a lot of research on HorrorLand. They learned about the dangers in store for its visitors, kept their own blog about it, and even posted a copy of the HorrorLand Welcome Guide online. And now, they've formally published that same guide, including all their notes and comments, as a warning to would-be visitors to HorrorLand.
Goosebumps HorrorLand Second Arc: Books 13-19
Online bookstores have posted a listing for more upcoming Goosebumps HorrorLand books, beginning with "When The Ghost Dog Howls", set to be released on January 1, 2010. They have provided the following synopsis, implying that the series has been extended to include nineteen books with a new seven-book story arc:
Each eerie adventure of the next seven-book arc begins with a trip to the Chiller House, a gift shop only found in HorrorLand. Kids are invited to take a little horror home with them and given a souvenir and a miniature Horror. At home, the kids experience wild things with their "free" gift, while the glowing, menacing Horror keeps an eye on the fun. When it's time for their payment, the Horror takes them back to shopkeeper Jonathan Chiller.
Unlucky book #13 kicks off an entirely new type of terror that will keep you guessing and quaking until book #19.
Plot: Twelve-year-olds Andy and Marnie had a great week in HorrorLand, even though they were freaked out by Murder the Clown and a zombie mob. When the park's Chiller House store offers Andy a free souvenir he doesn't ask any questions - despite the shopkeeper saying he'd have to pay "next time you see me"... or that the souvenir hound's tooth is said to be haunted. He thinks it's worth the risk to have a dog's tooth that grants wishes, but when he hears howling in the night and Marnie starts behaving oddly, he thinks again about the gift from HorrorLand.
"INSTA-GRO Pet: Amaze your friends with this GIANT creature!"
Sam Waters and Lexi Blake
Hamsters and Mr. Fitz
Camp Nightmoon staff
Plot: Sam Waters is desperate for a pet, but his parents insist he must prove he's responsible. To do so he takes an after-school job in the Little Shop of Hamsters, but it turns out that the hamsters have a monstrous side. Could his HorrorLand souvenirs have anything to do with this? 
Plot: Jessica Bowen and Ryan Chang return home from a visit to HorrorLand, and bring along a souvenir: a two-headed coin, which transports them back in time to meet Prince Beaufort, the coin's original owner... and are faced with losing their heads, unless they can reunite the prince with HIS head!
Plot: On October 30, brother and sister Chris and Meg rescue a young child in a costume from a gang of bullies, only to discover the "kid" is really Weirdo, a smelly alien with a lot of disgusting habits, who promptly swears allegiance to them. On October 31, Weirdo's people invade Earth, and the twins find their souvenir from HorrorLand may be the only thing that can save or harm them!  In the second part of the story, Chris and Meg return to HorrorLand and meet the protagonists of the previous three books, and are sent on a mysterious mission by Jonathan Chiller.
Notes: This book is advertised as being "An extra-long, extra-scary Halloween Special Edition: a HorrorLand first!"
This book is the longest in the Goosebumps HorrorLand: Second Arc
Plot: Marco and Gabriella are fans of The Ooze, a graphic novel series about a mutant made of oil sludge, and Jonathan Chiller's shop happens to have a rare edition of The Wizard of Ooze - with instructions on how to gain your own super powers. But when Marco mentions the book at a comic convention, he finds himself pursued by some shady characters...
Plot: Ray Gordon loves scaring his wimpy brother Brandon, especially with the new dummy, Slappy, he got Chiller House in HorrorLand. His parents command him to stop or they'll cancel his New Year's Eve party, so why do weird things keep happening?
Notes:Slappy New Year was also the title of one of the cancelled Goosebumps Gold books, raising the possibility that R.L. Stine may try to recreate the other cancelled Gold books.
Amazon.com and Scholastic Rights and Co-Editions detail completely different plots for the novel; Stine confirmed the plot from the Amazon version as the correct one on his Twitter page on June 16, 2010.
This is the first HorrorLand book to have a companion reissue that is itself a sequel (to The Curse of the Mummy's Tomb, the fifth reissue).
The plot of the book may have been rewritten for this series.
All previous guests from Goosebumps HorrorLand #13-18
Jonathan Chiller, Murder the Clown, Chef Belcher, Mondo the Magical, three other HorrorLand denizens.
Plot: Jonathan Chiller told six of his customers that they could each take a souvenir home, and that they would pay him back the next time they saw him. Now, the time has come for him to collect. Now, the six kids must compete in a scavenger hunt, searching all of HorrorLand for six red chests that can each send one kid back to their home. But Chiller has no intention of letting them escape. In the guise of six of HorrorLand's most notorious denizens, he will be doing his best to block them at every turn... and in doing so, make sure the horror never ends.
Notes: R.L. Stine gave the title as Return to Chiller House on his Twitter feed. However, it was changed prior to the official release.
Goosebumps HorrorLand Third Arc: Books 20-26
Plot: Mickey and Amanda have been put in charge of their vacationing neighbors' cat, Bella. But when she escapes from the house and disappears, Amanda has an idea to replace the cat with a look-alike from the local pet store Cat Heaven. When the owner refuses to sell them the cat they pick out, they decide to steal it... but unfortunately, the cats at the store are more than what they seem.
The books have two additional tag lines on the back cover, in between the main tag line and the Ticket Tag line. I'm keeping them here for the sake of completeness, but won't be posting them on the main GBHL page. They are as follows: