Whichbook

This website helps you find books according to your tastes. On the left side they have dials where you can select exactly how much of something you want in your book. If you want it to be all happy, slide the dial all the way to happy and so on. Along with the mood of the book, you can also choose some parts of the story to find the perfect book to read.

They also have lists that have many books in them if you don't want to go through the hassle of specifics.