The Lost Kingdom of Bamarre by Gail Carson Levine is on sale at Kindle US for $1.99. Levine won a Newbery medal in 1998 for another book,
Ella Enchanted, so I'd expect this one to be pretty good too, and it gets 4.6 stars out of 5.0 at Kindle.
Kindle US:
https://www.amazon.com/dp/B01JYX7LUA