I believe this is the 4th edition. I know I read the 3rd edition a few years back and really enjoyed it,. Learned a lot of details on the mythos that I didn't know. My only concern is that the new publisher @chaosium.bsky.social might not allow them to add stuff from other publisher books.
@chaosium.bsky.socialThe Encyclopedia Cthuliana launches on October 28th.
chaosium.com
Releasing in October - The Encyclopedia Cthulhiana, the definitive guide to the Cthulhu Mythos
The Encyclopedia Cthulhiana is an essential resource for cosmic horror enthusiasts, gamers, and researchers. Learn the origins of the gods and monsters from the pantheons of H.P. Lovecraft and beyond....