The book is the account of one Union soldier, Bobrick's great-grandfather, Benjamin "Webb" Baker.
The author will visit The Early Show on Thursday to discuss the book that opens a personal window to his past. And he will bring to the studio what is believed to be the only surviving original letter written by Webb.
Bobrick says the book is a story constructed from about 90 letters written by Webb during the Civil War. Up until 1998, those letters were buried in the desks and trunks of various relatives of Bobrick for almost a century.
He recalls after writing about the American Revolution in the book "Angel in the Whirlwind," a second cousin wrote him about copies of letters Bobrick's great-grandfather had written during the Civil War. She offered to give it to the historian.
Bobrick says he was stunned by how remarkably vivid, eloquent and compelling the letters were — especially because Webb was uneducated.
Shortly after Webb died, one of his children compiled all the surviving letters and prepared a typescript in the hopes that they would be published, which never happened. But in 1917, at the height of World War I, a handful of excerpts were published in a sporting magazine called "The Outing" in hopes that their patriotism would encourage young men to enlist in the army.
In "Testament," Bobrick uses Webb's letters as his guide and timeline. He fills in the history of the Civil War around his great-grandfather's letters — showing one patriotic Union soldier's view of the war as well as the big picture surrounding him.
Bobrick says Webb's story enlarged his understanding of the war, and the humanity of it.
Read an excerpt from Chapter Eight. Click here.