The movie is well known--though, sadly, it has become a one-word joke about sodomy in our popular culture--but you may not be aware that the book is equally highly regarded, appearing on Time's 100 Greatest Books Since 1923 list. The author, James Dickey, was best known as a poet before the publication of Deliverance, and accordingly he gives the book a sense of hideous wonder, preventing it from becoming the plain sort of thriller the topic might suggest.
Deliverance is a book about primitivism, the way it remains in us like a reservoir waiting to be tapped. At the end of the book, the dead lie at the bottom of the river which is about to be dammed into a lake, suggesting that the primitive part of all of us that remains from our ancestors lies dormant beneath what society makes out of us. What it brings out in Ed Gentry, the main character, is both amazing and awful: the power to survive as well as the power to kill. Perhaps the most frightening part occurs when Ed waits in a tree with a bow and arrow for one of the molestors, who plans on returning and shooting the suburbanites, and forces his mind and the molestor's to merge so that he might anticipate where and when he will return. Ed is forced to recognize that what the rednecks do to them, their violence and perversion, is not something that they possess alone but something that dwells within himself, and is necessary to survive in this backwoods Southern jungle.
This brings my total from the Times List to 22. I'd like to read them all, but I don't think I could sit through Infinite Jest.