Well the problem with that is that any book that's like that and is happy all the time doesn't like to be published. People don't want to read books about happiness all the time, it wouldn't be interesting. Tuesdays with Morrie is a good read, though it's sad. The Life of Pi is an interesting book, not depressing, but not particularly happy and inspirational. It's about stories, truth, and lies. There's always the kite runner and a thousand splendid suns, but they aren't particularly happy either (but I absolutely love them and endorse them). You might look up one of Jodi Piccoult's older books. They tend to be much happier than her new ones (though I'm not sure about the ones published after Nineteen Minutes).