I had problem with task given by Urag gro-Shub (he is sitting in The Arcaneum in Winterhold). He requested to bring him book “Hanging Gardens”. Problem was that at some point, before I got quest from him, I did get that book. Regardless that quest couldn’t be completed.
If that happens only solution is to enforce book to be dropped using codes:
- player.drop 1AD08 1 – drops the book “Hanging Gardens” even is quest for that is already started
Once book is dropped pick it up and quest will move on.