Always glad to see another Catton fan. "A Stillness at Appomattox" is so good it gives me goose-bumps.
I made my way through Shelby Foote's trilogy once, and I doubt I'll ever re-read it, but I go back to Catton time and again. I do love Shelby Foote's novel "Chickamauga." though...and his shorter Civil War books like "Stars in Their Courses: The Gettysburg Campaign."
I believe that book is an extended excerpt from Volume 2 of his Civil War trilogy.