Yeah, there's this series of little books (all by different authors, I think) about classic albums, and I bought the one about Zeppelin's #4 - it's pretty good, the guy talks extensively about the band's sorcerous, primordial sound, Page's obsession with Crowley-ana offstage and sonic thaumaturgy onstage, all that stuff. There's a great line about how the fourth album is "almost Lovecraftian in its namelessness", about how the band as a whole were like HPL to Black Sabbath's Robert E. Howard, and a very cool psychoanalysis of the music, lyrics and production (with about equal importance attached to each) on When the Levee Breaks, with reference to the events that inspired the Memphis Minnie original.
Plus there's quite a funny bit about some bloke who used to be a massive Zeppelin fan but saw them once when he was really stoned and thought that Page was "summoning demons" with his Theremin in the solo to Whole Lotta Love, then wrote this HUGE book about how Led Zeppelin were "the most dangerous group of Satanists active today" and had it self-published at huge personal expense. Now there's not many bands that have inspired THAT!