Mysterious Skin by Scott Heim

At the age of eight Brian Lackey is found bleeding under the crawl space of his house, having endured something so traumatic that he cannot remember an entire five–hour period of time.

During the following years he slowly recalls details from that night, but these fragments are not enough to explain what happened to him, and he begins to believe that he may have been the victim of an alien encounter. Neil McCormick is fully aware of the events from that summer of 1981. Wise beyond his years, curious about his developing sexuality, Neil found what he perceived to be love and guidance from his baseball coach. Now, ten years later, he is a teenage hustler, a terrorist of sorts, unaware of the dangerous path his life is taking. His recklessness is governed by idealized memories of his coach, memories that unexpectedly change when Brian comes to Neil for help and, ultimately, the truth.