Robert McCammon’s first published book!
I’ve been a fan of McCammon since Boy’s Life – one of my all-time favourite books.
Baal being his first, I find it is rough and not very polished, and has a few jarring bits of writing. Especially at the start. Once he finds his stride it isn’t bad. So glad he kept writing.
heretherebespiders 
genre? Looks like horror?
I’d give it that, possibly. More psychological and what if? Hard to classify. But Boy’s Life – that is one not to miss.
If books are in any way horror I avoid, period.
Oh, it has very heavy ideals about religion, but didn’t do quite what I wanted.