While I knew that Tolkien and Lewis had a close relationship, and that Tolkien was a big help in bringing Lewis back to Christianity, this book did a fantastic job drawing together much of how the war and their beliefs shaped their books. While many know Narnia to have an underlying Christian story, they don't realize LoTR also has its roots in Christianity. Well worth a read if you want to see the ties between the 2 book series, Christianity and the war.