I’m not sure how many middle grade and YA books I own. I’m sort of afraid to count. I’ve sorted them in lots of ways over the years, for my personal use and for my classroom. I've tried book-scanning apps, rainbow-fication, and assorted shelving configurations.
Here’s the system that has worked best for me for the past several years:
The short version – I classify my books into (mostly) genre-based tubs, code the book spines with patterned washi tape, and match the tub label card with the same washi tape pattern. I teach my students what types of books they can find in each category, and how to take care of the books as they search and return them. The long version, below, may help address details if you want to try this system.
I've had the privilege of working with hundreds of students and families in IA, CT, NC, MO, TX, and Canada.