1. Turmoil on the Rio Grande: The Territorial History of the Mesilla Valley, 1846-1865 by William S. Kiser (TAMU Press, 2011).
The region experienced much in the way of conflict during the mid-19th century, from battles and boundary disputes between the U.S. and Mexico through a Confederate invasion during the Civil War.
2. Confederate "Tales of the War" in the Trans-Mississippi, Part 2 1862 edited by Michael Banasik (Camp Pope Pub., 2011).
Read a short description here. Part 1 was very good and I look forward to all new volumes from this sub-series of Camp Pope's indispensable Unwritten Chapters of the Civil War West of the River series.
3. Lincoln and the Election of 1860 by Michael S. Green (SIUP, 2011).
4. Abraham Lincoln and Horace Greeley by Gregory A. Borchard (SIUP, 2011).
These two are new volumes from Southern Illinois Univ. Press's Concise Lincoln Library series.
5. Plenty of Blame to Go Around: Jeb Stuart's Controversial Ride to Gettysburg by Eric J. Wittenberg and J. David Petruzzi (Savas Beatie, 2011).
Undoubtedly at least partially inspired by the Sesquicentennial, paperback reprints of both old and recent titles are being released across the board at a vastly increased scale and clip. A great book, Plenty of Blame is certainly worthy.