It is said that more books have been written about the Battle of Little Bighorn than that of the Battle of Gettysburg. I decided to try one of the more recent entries.
James Donovan's "A Terrible Glory: Custer and the Little Bighorn: The Last Great Battle" is a superb, in-depth narrative of the Battle of Little Bighorn and the events leading up to it. Donovan's style is almost movie-like in describing the 7th Cavalry's fight against the Sioux. My only complaint is the lack of detailed maps, but almost every book has this issue.