Long was born a Catholic in Waterford in 1932. He lived in a thatched house with his immediate and extended family, including his mother, father, brother and his mother's parents. His father was a grower of vegetables. Long was fond of reading as a child, devouring Henry David Thoreau, Henry Wadsworth Longfellow and Zane Grey, and encountering trouble at school while reading when he was supposed to be paying close attention to his religious studies. His time at a boarding school was funded by a family friend but he quit after two years. He attended a Congregation of Christian Brothers school in Tramore but quit that as well, at the age of 14. He married a wife, Peg, and they had two sons and two daughters.
Bright Light, White Water, published in 1993, documented the history of every Irish lighthouse and their keepers off the Irish coast, with Long living inside Howth's Baily lighthouse while writing. Then he underwent a heart attack and a transplant followed in 1994. The transplant and recuperation received public interest – RTÉ filmed a documentary and Long's book, Change of Heart, described what had happened and advocated increased donor awareness. He was able to write and edit further books, completing his memoirs shortly before his death in 2010.