I would say it is a good book in regards to the movements of the troops, and how they enter the Custer battle. I might point out that he was not the founder of this idea of a skirmish at Blummers ridge. What would be interesting is if they would test those shells and find out the movement of the individuals as they went onto the last stand hill.
You might find that it is slanted to the Crow version of the battle....The Crows were in cahoots with the Sioux-Cheyenne and led Custer into a trap, and that leads to his ending of Bouyer killing Custer.
There is enough good stuff in it to justify reading it. Proceed with caution.