Is the John Oxenberger character based on Turner?

I read that Turner wrote HCL based on personal experience. Not having read the book, is it written from John's pov? I couldn't help notice that john is the only guy who gets the writer's (and consequently the film character's) sympathy, plus he's a writer. Does anyone know if Turner was (or is) a bass player? (Also, being one, he could be a fan of the Who's John Entwistle a.k.a "the ox")