The classics I find will stand up to repeated readings. I've read Middlemarch twice, Jane Eyre at least three times, Wuthering Heights a few times, Pride and Prejudice twice. They're like favourite holiday spots I can go back to over and over.
I'm also a huge - HUGE - fan of Iris Murdoch, and I'm currently on my second go-round of all her books. I've now re-read The Book and the Brotherhood, The Black Prince, and The Sacred and Profane Love Machine, and I'm halfway through An Accidental Man for the second time. I find now that I'm less absorbed in the plot (and all those disastrous love affairs) I can see more of the incredible philosophical thought behind the stories. And the writing itself is just so beautiful.