The Door in the Wall, by Marguerite de Angeli, takes place during the Middle Ages, much like Crispin: The Cross of Lead. Crispin is much more suspenseful and adventurous, whereas this book's suspense and adventure seems to be at a calmer level. This story follows Robin, a boy who is supposed to grow up to be a knight, but becomes ill and loses the use of his legs. Since his parents are living far away from him, he has been looked after by priests in the church. Robin learns to appreciate his life and eventually saves his uncle's castle from invasion.
It's a pretty good book for one that has a setting in the Middle Ages (few novels take place at that time, unfortunately, since we teach a Middle Ages unit in Social Studies at our school. However, it is not the most exciting book in the world, since he's bedridden throughout the majority of the story. The best thing I took away from reading about the friar teaching Robin about how to persevere throughout his frustration of being ill was his encouragement to find "the door in the wall." This meant that to overcome a challenge, one must never give up in finding a way through a wall. This is great advice for all of us in the struggles in our lives.