I've never really thought about this before...
I'm pretty sure I scored as high on the English portion as I did on the SAT when I was in high school because of Davey lol.
As for books? Not books specifically, but I had never heard of Baudelaire before I learned it's his poem "De Profundis Clamavi" (which is amazing and I can see how Davey's lyrics have been so influenced by him) that Davey recites in Midnight Sun. Baudelaire is now one of my favorite poets.
Eh...not really bands per se, but in general AFI made me become interested in music in a way I hadn't been earlier in my life. I mean I had always liked music, but it was so very restricted by my parents. Really anything heavier than the Beatles was "the devil" to them.
So yeah, I began really exploring bands that shared similarities with AFI in some way, which led me to hardcore punk and then early punk rock and the underground scene that was happening in New York in the early 70s (the Velvet Underground, the New York Dolls, Richard Hell, etc.)...later I really got into metal, and I still thank AFI for that.
Speaking of Sisters of Mercy - I can't say I'm a fan of their sound, but I do quite like early Paradise Lost, who was very influenced by them. Here is their cover of "Walk Away". I think it's fantastic. I love their guitar tone from their earlier days. Perhaps you've seen this before and that's why you assumed Sisters of Mercy were metal?