The book was a bit dry and jumped around quite a bit both in time and space. There was little effort in telling a coherent and engaging narrative.
But far more impactful was that it exploded the myth of the Texas Rangers, showing that far too many of them were just thugs and then providing a summation that lauds their contributions to Texas. I'm sorry, what?! Did the author not read his own book? And, seeing that so many innocent bystanders were robbed or killed by the rangers, largely for being Hispanic, undercut the notion that they were ever a force for good (even the Army hated working "with" them). As a fan of Lonesome Dove, I walked away disappointed at Larry McMurtry for romanticizing the Rangers and making them seem noble.
And, as a side note, I knew very little about Texas's history, so was surprised to learn that the state which doesn't want anyone to tread on them begged the U.S. to annex them. Multiple times ('cause they were broke). And Remember the Alamo? Why would Americans care about the Alamo? It wasn't even in America, it was part of Mexico, and became part of the Republic of Texas, which only lasted around ten years [see above for what happened next!].