There is a small chance that bookcases can contain spell books. I got a Burning Wall spell book from Mardaneus' house my first game, which was the only way I could defeat the giant spider in one of the rooms at the bottom of the catacombs (though I only used it a couple times after that).
In the first encounter with Zandalor, the dragon rider he kills dropped a gold strength charm. I saved and reloaded a save before the encounter a couple times, wondering if it was random or I got a strength charm because I was playing a warrior. I didn't get anything else drop, so reloaded the save with the charm.
After exploring near the castle, the knight you can fight there (depending on your conversation options) dropped a two handed sword that I needed to wait until I went up a level in order to equip (putting the stat points into strength and using the gold strength charm in order to meet the requirements).
