I’ve read Joyce’s Ulysses three times all the way through, and one other partial trip. I try not to go more than a couple of years without re-reading Tristram Shandy, or King Lear – probably pushing ten times each on those. Bulgakov’s The Master and Margarita I’ve read at least eight or nine times, though the last few have been in different translations – not sure if that counts as “re-reading” since there are significant textual differences between the different versions. I’ve done Pynchon’s Gravity’s Rainbow three times, and The Crying of Lot 49 several times – did one of my better grad school papers on it and have always enjoyed rereading it – but only once each for V and Vineland, and have yet to make it through Mason & Dixon or the newest one.
It hardly matters whether I’ve read something by Wodehouse or Waugh before; if the whim bites, I’ll do it again – Waugh’s novels I’ve read at least twice each, and most of Wodehouse more often than that. Someone else mentioned George MacDonald Fraser’s Flashman novels – I’ve read all of them twice now. Likewise for Patrick O’Brian’s Aubrey/Maturin novels, and I expect I’ll work my way through them again someday. There’s a handful of Tom Sharpe novels (Riotous Assembly, Indecent Exposure, and The Great Pursuit) that I’ve read at least twice. Most of Douglas Adams’ stuff I’ve read more than once. I’m seriously thinking about starting my second pass through Jasper Fforde’s Thursday Next books.
In non-fiction, the one book that I’ve re-read and continued to find rewarding is Daniel Dennett’s Darwin’s Dangerous Idea. It’s the most informationally dense book I’ve ever read that actually pays off the effort to work through it. The first time I read it it took me eight weeks or so of fairly concentrated lunchtime and after-work reading to get through it. The second time was much faster – I think it only took me six weeks. The third time I think I got it down to a month. I may take it on again sometime this year. There are a few other non-fiction authors whose stuff I keep coming back to: Malcolm Gladwell, Steven Johnson (particularly Mind Wide Open), Matt Ridley.