What book do I need to re-enter Candlekeep, and where do I get it?

What book do I need to re-enter Candlekeep, and where do I get it?

Solution 1:

You need the book History of the Nether Scrolls to get back into Candlekeep. You get this book from Duke Eltan at the end of Chapter 5 after dealing with the Iron Throne and reporting back to him. I think him giving you the book actually triggers the end of the chapter.

If you're having trouble getting Eltan to give you the book and you've already dealt with the Iron Throne and found proof of their misdeeds, play around with his dialog options. You need to tell him about Reiltar to trigger him giving you the book.