The problem isn't the means, it's the execution. They already do have plenty of books in circulation. Some out here are arguing that the books should be enough or that the players should research who Shar is on their own.
The other side of it is that some think that there should be some cutscene or something that explains who Shar is, at least giving some basic knowledge and information to the player so when Shadowheart does her "big reveal" the player isn't wondering, "Shar who?"
Sometimes I wish the plot would be more focused. They could have created a fine story, or the beginning of a larger story, on the Shar vs Selûne premise. The goddesses of Light and Darkness and their Clergy battling it out hundreds of years ago would have made for an amazing opening cinematic without spoiling any of the plot. It would have also set the stage for Shadowhearts big reveal.
There's just so many ingredients and factions in the BG3 plot right from the start it's really difficult to focus.
