This is another difficult one, because I usually expect to like every book I read.
That said, I forced myself to start War and Peace just because. And I ended up loving it. But I already talked about War and Peace and how I was able to get through it in my best read of 2012 post.
I somehow ended up either disliking or not being impressed with over half of French authors I've read. So I didn't expect to like Bel Ami as much as I did. And most definitely didn't expect to fall in love with Proust.
Another book I didn't expect to like is The Hunchback of Notre-Dame. Mind you, I'm not loving it either. I might have loved it if Hugo wasn't a pompous ass and didn't feel like climbing on that damned soapbox every odd chapter. (Seriously considering wasting time attempting to produce a Hipster Hugo gif to go in the review.)
Huh. I guess I came up with enough material after all.