Books can appeal to any age group. Make sure you include books from a wide range of genres, and don’t forget the comics! In addition to books that students can read, add activity books such as coloring books, crossword puzzles, and word searches.
There are many ways to run this reward !
You can even let students return books for some points back, kind of like when you sell your books back to a used book store. This will create a classroom economy based on books, and that's pretty awesome.