I agree with everyone here who's saying the dialog is messed up here. I've said so in other threads too. This is one of the things in BG3 thus far that really pisses me off. The PC is being seriously railroaded into either being a complete ignoramous idiot who shrugs and says whatever, or else a crazy person who screams about lying, when no lying has truly happened. And no, reading the books should not be the default for knowing things. In the context of the game, it is eminently reasonable that a character within that setting would not be spending their time picking up and reading every book they come across. Furthermore, even reading the books doesn't square with this issue because this particular dialog exchange comes quite early in Act 1, before you get to read many of those books anyway.
I know some of you disagree, but I think the greatest weakness in BG3 right now is rather poor quality of writing (across the board). Too much resources are being spent/wasted on silly gimmicks and "coolness" at the expense of the bread and butter of a good RPG: the writing.
