Hell House by Richard Matheson
The book while having been written in 1970 was mostly untouched by the passing of time. A few places in which it fell short were pretty important to the entire plot concept. Things they may be perceived as perverse or obscene in 1970 are much more widely accepted now. So if you can look past that, the story holds up fairly well. The book is pretty heavy in adult themes, so much so that I wouldnt even recommend it for teens. But if you're an adult who likes horror and can handle a lil depraved sexual undertone, then this book is for you. Also, it had been adapted for the screen in 1973 but I read that it might be remade soon.