An enormous list of 1000+ LitRPG series is available in one page, with click sortable headings.
LitRPG.Lo5.me
The list is focused on Audible, includes Kindle link, and GoodReads link and rating.
For people who like Tier rankings and book covers there are two synthetic rankings of the top half of the same list available at:
Tier#A
Tier#B
What is LitRPG? I’m glad you asked: LitRPG has a number of definitions, most of which have the story line include game-like elements, hopefully along the lines of a role playing game to be more appropriate to the “RPG” part of LitRPG. Some readers insist there are regularly listed statistics or the characters in the book can view a command like screen to track progression. There is overlap with progression fantasy, which must include development of the character, typically: gaining levels of experience, as the story progresses. See the Wikipedia entry for LitRPG.