Odhanan
Adventurer
It depends indeed on how much the players know and care.
I believe, however, that no GM can have an understanding of a given game if he hasn't read its core rules and background and worked out how these two elements mesh together. Way too many GMs assume they know a game just by reading its background or assuming things with just a scanning of the core books. For instance, many D&D DMs out there just assume they know Third Edition D&D, both in rules and feel, from having played AD&D. It's a bit like thinking you know what's in the DMG 3.X because you've read the AD&D 1E's DMG. That's a gross mistake (and believe me, I know many such DMs).
Further, no GM in my opinion can fully understand what s/he's doing when houseruling a game s/he hasn't fully read and understood. Many such examples of bad houseruling exist in my opinion, starting by GMs reading a particular rule, not liking it from the get-go and modifying it right away without thinking of the "domino effect" it has on the rest of the game. This is especially true of the d20 System.
So, yes, I believe that to be a decent GM and run a particular game, you should at least have read its rules and understand them, if only to know what you're doing when you're discarding some of its components.
I believe, however, that no GM can have an understanding of a given game if he hasn't read its core rules and background and worked out how these two elements mesh together. Way too many GMs assume they know a game just by reading its background or assuming things with just a scanning of the core books. For instance, many D&D DMs out there just assume they know Third Edition D&D, both in rules and feel, from having played AD&D. It's a bit like thinking you know what's in the DMG 3.X because you've read the AD&D 1E's DMG. That's a gross mistake (and believe me, I know many such DMs).
Further, no GM in my opinion can fully understand what s/he's doing when houseruling a game s/he hasn't fully read and understood. Many such examples of bad houseruling exist in my opinion, starting by GMs reading a particular rule, not liking it from the get-go and modifying it right away without thinking of the "domino effect" it has on the rest of the game. This is especially true of the d20 System.
So, yes, I believe that to be a decent GM and run a particular game, you should at least have read its rules and understand them, if only to know what you're doing when you're discarding some of its components.