This book deals with races that live primarily in urban settings, specifically humans, half-orcs, and a new race called the Illumian, whose most notable features are the sigils that constantly orbit their heads. This book is centered around races, their human blood and the effects of this.
Many of the resources in Races of Destiny deal specifically with urban settings and nearly all have racial requirements.
Dave Noonan explains how the designers approached the subject matter in initial discussions and design: "A lot of our early discussions included the question, ". . . and then what?" In other words, it's one thing to notice that humans tend to be more broadly multicultural than elves or dwarves. But when you look at how broad that canvas of culture is in the real world, it's simply staggering. So then what? What does that incredible cultural diversity lead you to? In the case of the humans, one possible answer is that human cultures are effectively each a race in their own right, as different from one another (in everything but physiology) as elves are from dwarves."