It's weird, I've also had occasions when I've inexplicably stopped reading a book I was really enjoying. I read Book I of
Don Quixote about ten years ago or something, really loved it, got a few chapters into Book II and just ran out of steam for some reason. I think partly is was because I was reading the classic 300ish-year-old translation, which doesn't bother me at all as far as the language goes but has absolutely no paragraphing at all, which makes it quite hard work to read. I ought to have another go at it after I've finished
Tristram Shandy (which I've been reading in spurts since last spring

) since there's a definite similarity in the humour and tone, which I think isn't coincidental because apparently Laurence Sterne was a big fan of the book.
Cool that you're digging Lovecraft. His style is so unique, I mean he's got passages that genuinely make your skin creep with sublime horror or impart a real thrill of beauty and grandeur, and then he's got passages that just make you laugh out loud, often in the same story. I think his best by a mile is 'The Colour Out Of Space', but if you haven't read it already it might be a good idea to read a few of his other biggies (basically, the 'Great Texts' as listed by Houellebeqc) before reading that one, purely to avoid any sense of letdown. The 'Silver Key' stories are also absolute gems - there are parts in the second one that read for all the world like a trip report by someone who's just freebased a fuckton of DMT, which is kind of funny as I get the impression HPL was probably the sort who gets light-headed after a small glass of sherry.
If you'll permit a shameless plug, I wrote
a few words on HPL and materialism which you might find mildly diverting, although it's also about
Cyclonopedia (dunno if you read that).