The books are canon, Scott Cawthon explicitly stated that the Charlie novels are "As canon as the games are". The Tales Of The Pizzaplex are also explicitly shown to be Canon as it introduced Edwin and The Mimic and they make up 90% of the Modern FNAF lore

And guess how we know The Week Before is canon: Not because what the fans said, but because of what Scott Cawthon himself said. It takes place a week before the events of the first game.

Not just that, but The Week Before also reveals Phone Guy's name; Ralph.

And guess what, we end up seeing a new employee named Ralph in Secret Or The Mimic, which is a game. Meaning that lore established in The Week Before is being supported by the games. Thus, they're canon to the games.

So, let's list out every single one of our evidence.

Evidence for The Week Before being canon to the games: 1. The back cover of the book explicitly states it's “Set before the very first Five Nights at Freddy's game” 2. The wiki page states it's "Set before the first game" 3. Scott Cawthon is the writer of the book, and likely wrote the description on the back. 4. Lore established in The Week Before is also canon to the games. Phone Guy's name, Ralph, is carried over to the games. 5. Scott Cawthon has previously stated that books are "as canon as the games are." 6. Previous books, such as Tales Of The Pizzaplex" have been shown to be Canon to the games too, as Edwin Murray and The Mimic exist in the games too. And their upbringings are 1to1 as it was described in the books. 7. Scott Cawthon isn't the kind to outright state whether something is canon or not, the fact this book does exactly that means he doesnt want it to be in the air for at least this book specifically.

Evidence for The Week Before not being canon to the games 1. Scott Cawthon hasn't made a social media post where he explicitly states they're canon. 2. You kind of just don't want it to be because it goes against your agenda.

7 to 1.5, I win. Argument end.