It's essentially a thought experiment on how an American monarchy would work, and what calamity it would take to make Americans accept one. Here's a hint: the current debacle isn't bad enough.
The key point is that this monarchy doesn't try to overwrite America with a foreign sentiment, but takes things back to how they were before the Revolution,
with much more of the distributed control a monarch actually has.
The book succeeds in making that place believable, and somewhere you'd want to live (that bit about censoring the arts and having royal oversight of the academies is especially assuring). Though if you expect this version of the American Kingdom to banish xyz undesirable ethnicity, you'll be sorely disappointed. Though it's pleasing that the author acknowledges proper use of force to be necessary in getting things into order (including the implication that a literal gun might've been put to Congress's collective heads). There's also plenty of American trivia often glossed over in the approved history lessons, such as Prince Charlie being offered the throne of America at one point. The author has some self-admitted shortcomings to do with economics, but as I am not trained in those either, I couldn't tell you what those are.
Overall, it's a fun and educational book, and I highly recommend it.