You might be able to grab the spell book off the table and the knife in the chest with Telekinesis / Wizards Sight. The orb is just decoration, it is not good for anything. The only other way in if you miss the distraction provided by the minstrel is to kill Kistandalius, but since he sells spell books and charms it doesn't make much sense to do so for a single spell book (maybe wait until just before hitting the gong).