Best Practices for Cataloging Comics & Graphic Novels came out in early 2023: https://alair.ala.org/handle/11213/18623
Some important points:
Cont (in the Fixed Fields) should always be coded as 6 for "comics/graphic novels" AND Ills gets coded as a
Lots of great info in the document regarding other fixed fields such as LitF and Biog. It's a gentle reminder that just because it's illustrated, it can still be a biography or nonfiction
Include a note when there is no title page about where the title comes from
300: the phrase "chiefly illustrations" is no longer allowed under current RDA rules, so add a note if something about the illustrations feels important
All graphic novels, graphic nonfiction and comics get two 336 fields
336 __ $a text $b txt $2 rdacontent AND
336 __ $a still image $b sti $2 rdacontent
Add a 380 for form of work
example: 380 __ $a Nonfiction comics $2 lcgft
Add a 586 if the comic won an award!
Per Library of Congress Subject Heading Manual instruction H 1430 section 2c, the LCSH form subdivision $v Comic books, strips, etc. is used for both fiction and nonfiction works
Not included in this document is how to handle call numbers. The following call number conventions for nonfiction and fiction graphic works was followed for the SEL Graphic Medicine collection:
Best practice in the past has been to catalog nonfiction comics under their subject heading
If a graphic nonfiction title is about the 9-11 Report, catalog it under HV6432.7 for Terrorism -- Specific country -- United States -- Specific incidents -- September 11 Terrorist Attacks 2001. If a nonfiction comic is a biography of the jazz musician, Charlie Parker, catalog under ML419.P4
Fiction graphic novels and comics are cataloged under their country of origin, not by author last name. For example:
PN6765-6768 for graphic novels by Italian authors
PN6725-6728 for American authors