SOLVED. Adult Fantasy. Knight searching for dragon whose hoard is books. Spoiler.

[Laura]

Plot:
Knight hired to kill a dragon and keep it from stealing the kings money. Female (in human form) ends up injuring knight when steeling the money. She keeps the knight with her at her hoard for several days before releasing him. Her hoard is made up of books. The knight wishes to become her partner, she challenges him to find her after she releases him.

Spoiler: Knight ends up opening a bookstore to lure dragon to him

I believe that in the same series there is a book about someone whose hoard is stones/gemstones.
Read this story in the last 1-2 years, unsure how new the book was at the time.

[Laura]

I found it!
Books & Broadswords, Volume One
Jessie Mihalik