We ordered book bins from Really Good Stuff and put them on book carts. This made the books easy to retrieve and also to move around the cafeteria if needed. We collected book donations from teachers and parents and sorted them by (approximate) grade level. Labels on the book bins let kids know which bins were most appropriate for their grade. One helper in each class was designated to pick up a book bin, put it at the end of the cafeteria table, and return it at the end of lunch each day.
On any day in our school cafeteria, kids are reading and talking about books. Here are some pictures I recently took of a few of my first grade friends reading and eating Doritos at lunch.