Right now I'm finishing House Of Leaves (Mark Z. Danielewski) for the 14th time, and I still am blown away by it. When I'm finished with that, I think I'm going to move on to Cloud Atlas (David Mitchell) and then reread The Raw Shark Texts (Steven Hall). Each of these may be described as hard to read, but when you put forth the effort, they are incredibly well structrued and written books, they'll be in my library for a long time.
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