The Last Stand by Nathaniel Philbrick. About Little Big Horn, of course. I don’t know how definite this account of the battle is (I’ve read Son of the Morning Star, but too long ago), but wow, Philbrick has read everything about everything. My own two big takeaways: 1) had Reno been more aggressive and run through the village things might have been different, 2) an integral part of Custer’s strategy was to take hostages, as he had done at the Battle of the Washita, 1868. Philbrick points out that if Custer had moved away from the river and joined Keough on Calhoun Hill, then taking hostages would no longer have been an opinion. @Tom McAndrew you’d like this, I found the end notes to be as fascinating as the book itself.
I've been tempted to read this book, as everything he's written about the American Revolution has been first rate. While he's not a historian as a career (i.e., ,an academic), he does a phenomenal amount of research for his books, and then has the gift of being able to write in a captivating, and quite interesting manner, which makes his books very informative, and enjoyable to read.