Disclosure: I received complimentary products to facilitate this post. All opinions are my own.
My older daughter really enjoyed Book Scavenger, a book about Emily, a girl who moves to the hometown of her favorite author, creator of the game Book Scavenger. In the game, books are hidden all over the place, and people solve clues to figure it out. This description alone was enough to intrigue my daughter, as she loves anything to do with books. Unfortunately, the author is attacked, leaving a mystery behind about the newest game. Emily, with the help of her new friend James, race to unravel the mystery before they get attached as well.
The mystery was fun for my daughter (and myself) to read. There was just enough element of suspense and danger to keep it interesting, without being too scary for kids. It's fun for adults who like to read young adult literature as well. It's a fast-moving book, so it's a very easy read.
And, of course, hiding the books is a thing. Get in on the fun and look to see if there's one hidden near you!