Thank you very much for posting the pictures, Faerith. That looks like the second balcony, not the lowest one. The lowest balcony is at about the level of an outside roof (the second roof from the bottom). Your first picture does not show this roof. Also, the tower is too narrow at that height, and each side of the balcony is too short. It is not the balcony that is reachable from the stack of books, you have reached a higher balcony.
Could you perhaps have a look downwards, please?