This is tough, because I read so many books I'd give 4 or 4.5 stars for but not 5, because I always find some aspect of the book that holds me back. For example, I just read Iris Murdoch's A Fairly Honorable Defeat and it was great, but the ending was just too ruthlessly cruel to me. So it was yet another book I admire but not love.
The last 5 star book for me was Time Traveler's Wife. It's not perfect and if I re-read it I'll probably find things that bug me, but as I was reading it I was swept away and it ended very satisfyingly for me.