A book you thought you wouldn't like but ended up loving.
There are several on an equal footing...
"Villette" by Charlotte Brontë
"Les Hommes protégés" by Robert Merle
"Don Quixotte de La Manche" by Miguel De Cervantes Saavedra
"Middlemarch" by George Eliot
A special mention goes to "The Fog" by Jeff Mann. I thought I'd end up disliking it for so many reasons, but in the end I couldn't but love the tale of these dirty bears.