You can use the following list of Library of Congress headings to perform subject-based searches for examples of and books about comics and related topics in all library catalogs. Results will include comics and graphic novels, as well as works of criticism about them.
You can also search for specific characters and creators as subjects (e.g., "Wonder Woman" or "Lee, Stan"). Or you can browse parts of collection on the third floor or in the Juvenile section. Call numbers to look for are:
The Best American Comics 2019 by 
Black Comix Returns by 
A History of Women Cartoonists by