I'll blame Alison if you and I become addicted to this. It's called The Book Seer. Type in a book you like, and it really does come up with books (recommended by Amazon and LibraryThing) that are similar. At least it did for me. I typed in the title of the most recent book I completed, which I read for the Women Unbound reading challenge, and this site did indeed suggest a number of others that would be appropriate for that subject. So go have a little fun with it.