The Two Princesses of Bamarre by Gail Carson Levine

Gail Carson Levine left her mark on fantasy with her well-loved Newbery Honor Book Ella Enchanted. Now she has created another shimmering and tapestried landscape of fantasy and fairies. 

The two princesses of Bamarre couldn't be more different. Princess Addie is fearful and shy. Her deepest wish is for safety. Princess Meryl is bold and brave. Her deepest wish is to save the kingdom of Bamarre. They are sisters, and they mean the world to each other.

Then disaster strikes, and Addie—terrified and unprepared—sets out on a perilous quest. In her path are monsters of Bamarre: ogres, specters, gryphons, and dragons.

Addie must battle them, but time is running out, and the sisters' lives—and Barmarre's fate—hang in the balance.