I would recommend my favorite book other than Harry Potter, The 10th Kingdom to Luna Lovegood because it is a great fantasy novel about the universe, where we live in one kingdom (which is earth) and there are nine other kingdoms but they have to do with fairy tales. It really is a great book! I think of all people she would appreciate it as much as I do.
Also I think I would recommend the book MORE THAN A PINK CADILLAC to Hermione Granger. This book is one that I read as a beauty consultant and was a bit wary at first. But going through it there are so many awesome ideas and life skills and so much to learn. I would love to know what Hermione thought about the book and such.
I'd recommend Jemima J by Jane Green to Hermione. It's a story about learning to love yourself, no matter what you look like. Hermione is surely not a self-hater, but what teenage girl doesn't have self-esteem issues? :P
Discworld to Hermione. The girl seriously needs to loosen up. And maybe Good Omens to Luna, except I'd tell her it's a documentary. Watching her fit it into RL would be hilarious.