If plays count as books, then most of Shakespeare’s plays. I’ve already reread a number of them (e.g. Hamlet, Macbeth, Merchant of Venice, and A Midsummer Night’s Dream.)
I’ve read Whitman’s Leaves of Grass, a couple times in full (and segments of it many times over) and expect to get to it again. I’ve read Voltaire’s Candide a couple times.
I could definitely see rereading Journey to the West, Water Margin, and Romance of the Three Kingdoms, but at this point I’m hoping my Mandarin will get good enough to read them in Simplified Chinese.
I’ve read a number of nonfiction texts multiple times — e.g. Sunzi’s Art of War, Miyamoto Musashi’s Book of Five Rings, Laozi’s Dao De Jing, and Emerson’s Selected Essays.
I’m generally not a fan of rereading books because there is so much awesome stuff out there to be read a first time. For all the reading I’ve done, there is still a massive number of classics that I have yet to touch. Usually there has to be a good reason for a reread, e.g. a new translation that promises to be improved / simplified, the book is just so potent as to still have lessons packed in after the first read, it’s a challenging read and the first go leaves a lot on the table, or — like The Little Prince — its enjoyment-to-time investment ratio is high.
Tiger Riding for Beginners 
“Buddenbrooks”.
Obviously still the same book as in 1901 in German, but they say that a third translation into English is in progress. To me, it’s really one of the novels that keep providing lessons – and enjoyment.
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