This is the third book in the Princess Diaries series. These are definitely teen girl books, and not the truly any age books that some are, like the Harry Potter Series, or the Anne of Green Gables series, or the Little House series.
She spent the entire book agonizing about whether a certain boy liked her. While at the same time getting ready for finals and dealing with princess training and all the other events in her life. Not that they are bad, by any means, they are pretty good, you just have to consider the target age when reading them.