So far I have
- 4e
- Apocalypse World
- 5E
- Blades in the Dark
- Heart
- The Mothership Wardens Manual
- Pathfinder 2E GMG
Are there any other heavily discussed tomes that I should pick out to read over?

A tabletop enthusiast, for better or worse.
Where to Find Me After Cohost:
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dungeon23: The Tree & The Tower
D&D: Old Flames
Break!!: Mossgrave
Erasure Adventure Prep
So far I have
Are there any other heavily discussed tomes that I should pick out to read over?
Fellowship, 100% https://preview.drivethrurpg.com/en/product/177662/Fellowship-2nd-Edition--A-Tabletop-Adventure-Game
It's a fantasy *world game with a focus on building a world together and bonds.
I have a friend who keeps me in constant awareness of fellowship 2e, but we’ve never discussed any of it’s GM stuff. I’ll check it out!
The Holmes Basic and the Moldvay-Cook Basic and Expert sets for D&D get brought-up a lot in the dungeon game scene. I read their BECMI successors and those are set-up to teach B/X D&D to both players and GMs in a way a lot of D&D books aren't.
They're not explicitly GMGs, but Aaron Allston's 1986 Strike Force supplement for Champions and the 1990 Campaign Sourcebook and Catacomb Guide by Jennell Jaquays and William Connors get cited as early published attempts to provide practical GMing advice. I think Robin Law also published stuff that did something similar in the 80s and 90s, but I'd have to go digging to confirm that.
If I remember, I'll page through my pdfs and books when I get home from work and add any others that come to mind here:
Is this like "Games often brought up in how they vary in running games" or "Things that get Discoursed about a lot" or just like "This game does neat things from the GM perspective"?
I’m looking for books that have good GM advice, which I am assessing based on how often they’re discussed.
Gary Gygax wrote a book about GMing called Master of the Game. it sucks.