If you need to delete a resource from your bookshelf, just follow these simple steps!
From your home screen, select Bookshelf.
Once you are in My Bookshelf click on the three dots next to the resource you would like to delete.
Otus will ask if you are sure you want to delete this resource from My Bookshelf.
Now that item is gone! Be careful, though. Resources you delete from your bookshelf are permanently gone.