Among the large number of available books about the Civil War, I would recommend several books presently available through Amazon.com or other dealers for additional background information specifically related to the soldiers of the 13th Maine Infantry,
To give the reader a better understanding of the soldiers of the 13th Maine and their activities. "The Life of Billy Yank" by Bell Irvin Wiley. (A companion to "The Life of Johnny Reb" by the same author.)
Almost forty of the soldiers of the 13th Maine received commissions in regiments of black soldiers in 1863. To learn about these officers and the men of those regiments I recommend reading "Forged in Battle, The Civil War Alliance of Black Soldiers and White Officers" by Joseph T. Glatthaar.
To gain a greater appreciation of the personal lives of the soldiers and their families back home I recommend "The Vacant Chair" by Reid Mitchell.
Several good books books about the war in Louisiana include: "The Capture of New Orleans 1862" by Chester G. Hearn, "Red River Campaign" by Ledwell H. Johnson, and "War Along the Bayous" by William Riley Brooksher.
"Benjamin Franklin Butler, The Damnedest Yankee" is good reading about a controversial character plus it adds insight into the incident concerning Chaplain Moore during the hurricane and provost duty at New Orleans.
"The Reminiscences of Neal Dow" is an autobiography published by The Evening Express Publishing Co., Portland, Maine, in 1898, with the last two supplemental chapters written after his death in 1897. It is out of print but may still be available in libraries and specialty book stores. (I bought a copy at the 20th Maine Shop in Freeport, Maine, in 2005 - Charles Bonsall.)
Finally, I recommend that the thorough student learn about the culture and history of the men of the period prior to the war through books like "Liberty Men and Great Proprietors" by Alan Taylor and "Liberty in Expansion, 1760-1850" by Oscar & Lilian Handlin.
See the "New History Project" to learn about a new history being written and the nature of a great deal of additional information soon to be available about the 13th Maine Infantry Regiment and the soldiers that served in the regiment.