I was given a quest to recover a book from High Gate Ruins, when I revered it I noticed that it was stolen. How to I clear this item? I tried to turn it in to the Arcaneum, but it doesn't show up in my inventory when I do.
You can try selling to a fence, or putting it in a container and letting a follower grab it, although since it's probably listed as a quest item, that won't work. I'd suggest that you reload a save from before entering High Gate Ruins, and then enter/complete the dungeon again. If it is still marked as stolen, reload again and wait ~10 days before coming back.