I tend to re-read the classics - Mill on the Floss (George Eliot) is one of my favourites and also Far from the Madding Crowd (Thomas Hardy). One that is in my head to re-read (again) though is Doris Lessing's Shikasta. Blew my mind the first time and I re-read it very quickly afterwards. I'm feeling the need again. I had only a vague understanding of the second one in the series though...
So far I've read 19...
I have some books that I reread every year.