I've found Unknown Book, Vol. 1 and sold it to Urag, but the objective 'Bring Ancient Falmer Tome to Urag-gro Shub' is still active. How can I get rid of it?
If you play on PC I'd try the console command:
So 0 should remove the quest from the log but would re-enable you to do the quest. Therefore I recommend trying maybe even 100, which used to be the standard
EDIT: Setting the quest's stage to 200 worked for kotekzot. This has been done with the console command: