Gravity's Rainbow by Thomas Pynchon. It has a well deserved reputation of impenetrability, and it takes a bit of mental adjustment to shift into the gear necessary to negotiate it. My first time through, at approx 20 was easily my third or fourth attempt at it, and was possible only because I forced myself to continue through it at a relatively normal pace without stopping too long to go "wha...." and try to figure out what was really going on. I would compare it to the reading version of what you have to do with your eyes to see those MagicEye images. It worked and I made it through after a few weeks and I think it is the book that in some way taught me to read other books, and I only actually arrived at that reflection as writing this, but it is a true statement. While the plot of the book is clearly discernible from beginning to end, the frequent shift of setting, characters, tone, voice, etc occurs nearly continuously, at least within the first section. Its like one of those movies where a different director shoots a single plot thread, only in this case its as though there were a different director for every scene or cut.
The quantity of invention on display for the 700-however many pages it consumes, is titanic. And the various pastiches that Pynchon pulls off with both accuracy and love are astonishingly numerous. Its like he was daring the world to come up with something he couldn't write and had so far come out on top. The additional pay off for all the work required to consume GR is that it is outrageously funny. Jokes and Broadway numbers performed transparently by the characters, complete with blocking directions straight out of Gene Kelly - Vincent Minnelli musical.
Gravity's Rainbow is one of those ciphers of modern American literature, in which the reality of it, and the cultural parodies it has inspired, like one of my other electrifying reads, IJ, almost perfectly balance. For every proto-hipster than insists that it is to be disregarded for its self indulgence and self-consciousness of pretensions, a serious reader who will stipulate to all of the above, but go on to acknowledge and assert that all the cultural baggage aside, there really is a THERE there.
I think its probably good that Pynchon writes so infrequently, because it prevents him from becoming his own self-parody. There is something remarkable to me about V., GR, Mason & Dixon, and to a lesser extent, ATD. They all exude an empathy with their characters, that is remarkable anywhere. I'm not sure what happened with Vineland, Inherent Vice, or The Bleeding Edge, except to say that though the plot devices and Pynchonian character names, which are frequently even more omnisciently specific than anyone since Dickens, can be entertaining, the characters themselves prompted zero interest or engagement with me. They are as pure a mechanical constructs. I felt with the first group, that it was clear and emotionally satisfying to me when Pynchon demonstrated that he cared for a given character, and it made reading them a transporting experience the first time around. I kept working to get myself emotionally invested in the characters of the second group only to fail for lack of purchase. I recall reading the DFW thought Pynchon a failed genius because he tended to trivialize his own work and never really betray any emotional engagement to the reader. I wonder if he was responding to the same thing I am describing.
Anyway, Gravity's Rainbow, way worth the hype, as well as the effort to complete it.