DaveMage
Slumbering in Tsar
Combining the Player and GM book (ala the Pathfinder Core Rulebook) makes a lot of sense from the publisher point of view (using Paizo/Pathfinder as an example):
1. Everybody buys the Core Rulebook, so everyone who plays will also have the guidelines on how to be a GM.
2. There are no big adventure (or monster) secrets in the core book, so being familiar with the material will have no significant impact regarding adventures.
3. More GMs = more sales, as GMs historically purchase more products than those who are just players.
If you split the books into a player book and a GM book, a lot fewer players will have access to the GM material, and thus, you've created a barrier to entry for GMs.
1. Everybody buys the Core Rulebook, so everyone who plays will also have the guidelines on how to be a GM.
2. There are no big adventure (or monster) secrets in the core book, so being familiar with the material will have no significant impact regarding adventures.
3. More GMs = more sales, as GMs historically purchase more products than those who are just players.
If you split the books into a player book and a GM book, a lot fewer players will have access to the GM material, and thus, you've created a barrier to entry for GMs.