I spent 15 months a few years back reading (in some cases re-reading) every one of Dickens' novels, plus his two travel books, all his short stories, and quite a big chunk of his social and political journalism. Read nothing else during that time - just Dickens! I have to say I loved it, and it really opened my eyes anew to London whenever I visited; but it's also true to say I doubt I'll ever look at Dickens again (with the possible exception of The Pickwick Papers)!
My personal literary nemesis was Ulysses. My first attempt to read it was in 1974. Tried reading it slowly with explanatory reading guides. Tried sprinting quickly through it. Never got past half-way. Finally after 33 years and half a dozen attempts, I managed it in 2007 - thanks to a 8-week 'Ulysses' class with reading homework each week. Yes it was worth it.
Edit: Oops. I see now my Ulysses comment should really have gone in the related thread, not this one. Sorry.