The Dr. Seuss Catalog: An Annotated Guide to Works by Theodor Geisel in All Media, Writings About Him, and Appearances of Characters and Places in the Books, Stories and Films

This is a great book for Dr. Seuss collectors! I collect old Dr. Seuss books and items as a casual hobby so being able to reference certain specifics about those books in here is very helpful. It also has neat information about some relatively unknown works of his that you might not otherwise be able to access. Outside of children's books, he also was involved with films, political cartoons, advertisements, etc.