Previous books I that have read about this topic include..
The Fellowship: The Literary Lives of the Inklings: J.R.R. Tolkien, C.S. Lewis, Owen Barfield, Charles Williams – Philip & Carol Zaleski.
A Hobbit, a Wardrobe, and a Great War: How J.R.R. Tolkien and C.S. Lewis Rediscovered Faith, Friendship, and Heroism in the Cataclysm of 1914-18 – Joseph Loconte
Tolkien's Faith: A Spiritual Biography – Holly Ordway
Tolkien And The Great War: The Threshold of Middle-earth – John Gareth [I loved reading this book after watching the Tolkien bio-pic on his early years!]
I own and have read most of Tolkien's Legendarium.
by philliplennon