Who is the "Other?"

I recently read this book for my book club. We had the discussion last night, a more rousing discussion than we typically have, this could have been because everyone present actually read the whole book. It also could have been because we didn't all agree on every point.

The book is about a friendship between two men, Neil Countryman and John William Barry. Neil is from an average, middle-class family and John William is a rich kid, with rich kid family problems and a mentally ill mother. The story starts when the boys are in high school in the 1970's and follows their friendship until John William's untimely death in the early 1980's. I say "untimely" death, but at that time John William had been living as a hermit in the Hoh Rain Forest on the Olympic Peninsula in Washington state for seven years. He probably wouldn't have lived that long if it hadn't been for Neil's forays into the hermit camp with necessities from civilization. In the end Neil is left with a huge surprise from his friend twenty-one years after his death.