On second thought, I think it's better to use a computer.

For example, when we buy things in a supermarket, everything in the supermarket has an electronic card with product information on it. If we leave without paying, the system will call the police.

Then, is it possible to put a small electronic information card in each book, and then there is a device similar to bus induction in front of each bookshelf? The computer pre-stores the information of each book on each shelf, and it is properly kept by a management system.

This is very convenient. When the customer returns the book and walks through the bookshelf with the book, the system detects the information and then gives a voice reminder. Please put the books on which floor and which compartment. Thank you.

If the system does not detect this information, it will remind you by voice. Sorry, your bookshelf is not like this. Please put the book back on a shelf. Thank you.

This naturally requires relevant capital and technical input, but once it is established, it is estimated that it will be much more convenient.

If you don't have this, you have to sort it manually, and the person in charge will check it and return it.