I have long been a reader of the history of the 7th Cavalry and its Western campaigns in the mid to late 19th century. Having lived near the Little Bighorn Battlefield, I have visited it and retraced the path of Custer's last battle on a number of occasions. I never tire of visiting the battlefield and I never tire of reading the latest written accounts of Custer's life and the events of the battle.
I recently stumbled across James Donovan's 2008 book, A Terrible Glory: Custer and the Little Bighorn--The Last Great Battle of the American West. Exhaustively researched and very well written, it is the first book with a fresh interpretation of the battle and the events leading up to it in a very long time. Donovan leaves no stone unturned (the endnotes alone cover 82 pages) and does a credible job of making a case that Custer was made a scapegoat by his direct command following the battle.
There are more technical works about the Battle of the Little Bighorn, but A Terrible Glory is an even-handed and very interesting narrative written from primary sources. It is the best and most comprehensive work I have read on this subject to date.
Another excellent treatment of this subject is Evan S. Connell's, Son of the Morning Star: Custer and the Little Bighorn , which is a delightful read, if somewhat meandering in style. This book was made into a less interesting movie, filmed, in part, a block from my former home in Billings, Montana.