The question of what sort of setting information will guide my choices is not primarily mine to make. I would agree that a good GM will work with their players to develop a canon that everyone is on board with, but it's technically the GM's privilege and responsibility to do so.
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I don't have a specific expectation of a right to tell the GM what sort of canon choices to make.
Different groups adopt different approaches to the distribution of authority in respect of setting, backstory etc.
Just to give one recent example from my own play: a month or so ago my group started a 4e Dark Sun game. The 4e Dark Sun campaign guide is set some indeterminate (but not all that long) time after the overthrow of the Sorcerer-King of Tyr, and it establishes Tyr as the default starting point for a campaign.
No one in my group (including me) has played Dark Sun before. I have the 4e books, and also have the original 2nd ed boxed set because another member of my group gave it to my a couple of years ago when he was cleaning out his bookshelves. (I don't know if he ever read it.)
The pre-game introduction to the setting was a few sentences by email circulated around the group: sword and planet; sand and sandals; arcane magic is defiling; no divine casting; and (in our game) bards and avengers are to be treated as psionic.
When a couple of the players wanted to play Eladrin, I also told them about the Lands Within the Wind - the Dark Sun version of the Feywild, which has been increasingly eroded due to the effects of defiling.
Then, when we actually had our first session, I asked each player to come up with a "kicker", that is (to quote from The Forge),
an event or realisation that the character has experienced just before play begins, which thereby propels the character into the game. The player of the half-giant barbarian stated his kicker more-or-less as follows:
I was about to cut off my opponent's head of in the arena, to the adulation of the crowd, when the announcement came that the Sorcerer-King was dead, and they all looked away.
So that settled the question of timelines: the campaign starts at the moment of the overthrow of the Sorcerer-King.
Which almost guarantees that our game is going to depart from some of the canon in the campaign book, because the series of events that follows the death of the Sorcerer-King will almost certainly be different in our game from what is set out in the book, in part because the PCs will probably be intimately involved in them.
I see this as a concrete illustration of [MENTION=6785785]hawkeyefan[/MENTION]'s point, that actual play in a setting precludes strict adherence to canon. I don't see how it could be otherwise, unless the GM is exercising an
extreme degree of control over the content of the shared fiction.
I view 'canon' as a kind of Platonic Ideal thing. There is, somewhere in the ether, a 'true' Eberron, that no one has ever written about in its entirety.
I understand the pull of Platonism in relation to mathematical truth, or even empirical truth. But not in the context of fictional creations, particularly fictional creations that are
intended primarily as the source of elements for others to deploy in their own authorial endeavours.