I think I'd have to go with the wedding people's choice, To Kill A Mockingbird, for fiction.
For non-fiction I'd choose either Gerald Durrell's My Family and Other Animals, for it's pure joyfulness, or Mr God, This Is Anna by Fynn. I have to agree with Raven though about book loves being so personal. Two of my friends who I recommended Mr God, This Is Anna to didn't like it much and I've read on here criticism of Durrell's book as being too idyllic.