Partly thanks to the Cthulhu Mythos Sale, several more supplements have reached a best-selling level. The following have all achieved the Copper sales level on DriveThruRPG
100 Books on Cryptozoology to Find on a Bookshelf
100 Detailed Items to Find in an Occultist’s Chambers
100 Irrelevant Clues to Bamboozle Players
Tomes of Alchemy
There are a number of other supplements that are not far off achieving this level.
Publishing RPG Supplements to Help GMs