Richard Perry is a First Person Central Narrator, but with a side helping of First Person Peripheral. As in, the guy's definitely at the center of the story—his feelings and emotions about the war are the main ones we get—but the story's about his fellow soldiers, too. That's why the book's called Fallen Angels, with an 's.'
There are episodes that aren't about Perry at all, like Monaco's hallucination or Gearhart's letter to his wife, which Perry only reads because Gearhart gives him a copy in case he dies before he can mail it. Morbid, but good planning.
Pro tip for authors: if you want to tell the story of many characters through the point of view of one, make your main character a quiet, introspective good listener—the sort of character others like to confide in. With Richard Perry, Walter Dean Myers has this method down.