I read the Forgotten Realms books for 3.5 like books because most of them is lore and not necessarily rules, and I think it was pretty dope back then. I would always use it for the basis of my campaigns, but I would place it somewhere that didn't have a lot of stuff already written about it so I could kinda of do my own thing while still having all the content and the ability to use things I didn't create if it made sense to do so.