The FRCS and PGtF aren't considered core books.
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'Players Guide to Faerun'
Faerun is a world on its own, just like all other ones.
Because the so-called 'Player's handbook' doesn't have most of the reaces as playable, I will not consider it as the Bilbe of RP-ing, and won't use the Greyhawk gods for all my clerics. That book was written clearly by people who use mostly the Greyhawk world for their story.
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Um, no. Only the PHB, DMG, and MM (I) are the core books. Everything else is considered by WotC to be optional.
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But see, they are for Greyhawk, even if not named like that. Even the gods listed in them are from Greyhawk.
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And? Your point? They are the core rulebooks as defined and stated by Wizards of the Coast. Josh's point is entirely correct.