Ambidextrist — Peter Rock

This provocative novel follows Scott, a lonely drifter who earns money as a medical test subject and finds shelter in abandoned buildings on the riverfront. He first befriends Ray, a mysterious homeless man whose tenderness can't hide his unsavory tastes; next, he sets four adolescent boys on a series of increasingly dangerous dares. As these relationships develop and tangle, Scott gains insight into various lives and proves he can outlast any bad first impression.