I just finished reading "Team of Rivals" by Doris Kerns. This book isn't new. It was published in 2005. IMHO, it's a "Must Read" if you are interested in the politics that led up to the Civil and Lincoln's government during the War. The title of the book is based on the fact that Lincoln put all his rivals for the Republican presidential nomination on his cabinet. In their own ways, Seward, Chase, Stanton, and Bates all did outstanding jobs during the War, all while competing with each other. And in the case of Chase, trying to replace Lincoln as President.

The book is long (750 pages.) but actually very readable. I would highly recommend the "Team of Rivals".