Lincoln and Grant’s Teamwork: Keys to Their Civil War Success by Edward H. Bonekemper, III
Basically the final chapter of Bonekemper’s largely fawning work Lincoln and Grant: The Westerners Who Won the Civil War, it does a lucid job of looking at the traits Lincoln and Grant each possessed that made them effective working partners. The foremost of these was trust. Lincoln trusted Grant’s military judgment even during trying times. Grant trusted Lincoln’s political judgment, even when it meant not getting everything he felt was needed to prosecute the war.
Though well written some of its assertions are a bit of a stretch. But, it is an area most Lincoln and Grant biographers don’t dive into in detail so is well worth the read.