Changing a block's texture depending on items it contains.

I am making a bookshelf block that can contain enchanted, written and regular books in it, and I want the texture of the bookshelf to show what books are in which slots. The base texture of the block would be an empty bookshelf. So if there's a book in the third slot, it appears on the block itself, where the third book would be placed on the vanilla texture. My original idea was to make an individual texture for each "state" of the block, but I'd have to do over 200 individual textures, so the same number of block "sates". Then i thought of simply adding an overlay texture, similar to how spider eyes eyes work. Is there a way to do that? If so, is it doable in the 2020.2 version? (using it for 1.12.2 compatibility)

Thanks in advance to anyone able to help me!