Found sturdy brown leather backpack with a hot air balloon patch in Balboa Park containing books and a water bottle.

I found a sturdy brown leather backpack lying on a bench in Balboa Park while enjoying a walk on Sunday afternoon. It looks well-loved, with some scratches on the surface, and it has a patch of a hot air balloon on the front. I opened it and saw a few books and a water bottle inside. If this belongs to you, please describe the contents so I can ensure it goes back to the rightful owner.