Gravity's Rainbow is the most difficult book I have ever read. In it, Pynchon weaves a fabulously dense web of paranoia, sexual conquest, and yin/yang. I can't claim to understand all of the symbolism (or even all of the plot, dammit!), but it was a wonderful experience to read a book on such a large scale in which every phrase is exquisitely crafted. I'm told that this book should be read more than once, and I look forward to having a second go at it at some time when I can devote a solid two weeks to it.