All of my children love books. We read daily and Sofiya is able to read beginner books by herself now. She and Walter both have their own library cards and love to go to the library to check out a whole pile of books. When they got their own cards, I wanted to make keeping track of their cards and books as simple as possible, so I made them each a library bag. They each already had their own decorated tote bags. To each of these, I put a keychain around the handle; the kids each chose a fun chain of their own. Then I added the handy key tag library card that our library gives out alongside the credit card sized card. If your library doesn’t use a key tag card, you could ask about punching a hole in the corner of a full size card.
And, voila! The cards can’t get lost because they are attached to the bags. The books the kids check out go into the bag as they are browsing, so they know how many they can check out. They come home in the bags. When they are taken out and read, they go back in the bags. They are stored in the bags until they are ready to go back to the library. And then the bags are toted back to the library to be emptied into the book return!