If you’ve read the dedication of John’s Peacemaking Under Fire, you know that one of his heroes was Major General George Henry Thomas, a Virginian who fought for the North in the Civil War and never received credit for his amazing accomplishments. John wished more people would become aware of Thomas. Either of these books will do that.
(1) Master of War, by Benson Bobrick.
(2) Rock of Chickamauga - The Life of General George H. Thomas, by Freeman Cleaves.