I sort my books by:
favorite authors (Roald Dahl, Beverly Cleary, etc),
favorite book series (A to Z Mysteries, Magic Tree House, etc),
favorite topics (animal stories, sports, etc),
nonfiction science (animals, earth science, space, etc),
nonfiction social studies (Revolutionary War, map skills, etc),
math (geometry, number sense, etc).
I also have a ton of books from the school that I put into this big white bookcase. I did pull out books that go along with my bins, but not a ton of them.
I used bins from the Dollar Tree in blue and green. Those colors match the major color scheme in my classroom. I also printed out library labels that I bought on TPT. I laminated them and then sticky tac them to the bins. This way I can change out different bins to meet the needs of my class that year. Some years the class loves Geronimo Stilton books so I make a bin for that. Some years it is a Junie B. Jones group so I switch that bin out. I don't like my bins permanent for that reason.
Do you sort your library?