The topic is of interest: given that today the Supreme Court is interpreting the constitution on the basis of the founders' intents. What were the founders' opinions on this. In particular, how did they behave?
The book tries to answer this question by examining the constitutional issues that came before the first and fifth Congresses. Since the constitution was new, they were forced to spend time deciding exactly what it meant, and indeed they did. The first Congress spent their first two months just debating a constitutional matter when things like debts were festering and taxes were going uncollected. That's how important they saw these matters.
The particular events/questions the book addreses:
1. Who had the power to fire department heads, the president, the president and senate, nobody, or something else?
2. Should amendments be added to the end or incorporated into the text? Was the original constitution (at that time only two years old) more of a living document or a sacred text? (That they opted for the sacred text idea has probably meant that it has not evolved as much as it might have. My own thought, not addressed in the book, is that on the other hand, interpolating texts probably would have been too difficult to propose to the public).
3. Was the government constitutionally able to incorporate a national bank? An interesting little point here is that the failure of the anti-bank forces led them to start the doctrine of popular opposition to the government, which led to the Jay treaty opposition, political parties and the Virginia and Kentucky Resolutions, which later influenced southern separatists. A lot of the way subsequent history developed came out of these early struggles when antagonists reached for whatever weapons that came to hand in attempting to win their struggles. Not that those kinds of developments wouldn't have come later anyway, but their origins are noticeable already here.
4. Did the House have any role to play in foreign treaties? (Jay treaty)
Unfortunately, the writing is very wordy and repetitive. Repeatedly, especially when a bunch of contemporary quotes are being cited, one wants to shout "Get on with it already!". It's important that arguments be solidly based on sentiments actually expressed, but quite prosaic to have to read through all of them. Maybe if all the quotes had been placed in optional to read side panels.
I recommend merely skimming the first two chapters, which set up the context and scene, for otherwise you may not finish the book at all. Only in chapter 3 does it become something that people other than constitutional lawyers want to read. Even then, there are far too many unnecessary words. As just a simple example, every time it mentions Senator William Maclay it cannot resist saying "the irascible William Maclay". We got it the first time. At least this one is only a single word. Elsewhere there are long clauses that could easily have been omitted because all they're doing is restating what was said in a previous paragraph.
There are also a lot of little things left out. Imagine spending a whole chapter on the bank controversy and never mentioning the famous meeting in the room where it happened. This is just one example. It also never mentions how Hamilton sabotaged the Jay treaty, or even the unconstitutionality of the Chief Justice taking on a second office as Envoy. But these are mere quibbles.
The conclusions suggest that today's constitution is mostly seen as fixed rather than flexible, which seems to suggest that the latter might be an option. I don't think it's only because that's what we're used to is the reason it's that way though. Human nature has played its role.
The idea of the book is great. The individual topics are interesting. In examining debates, it has the clever idea of examining what both sides are taking for granted and using this to chronicle undeniable changes in understanding, separate from the points of view. It also points out the danger that a constitution has to be based on words, but the meanings of words can change over time. But the book is also quite long and the writing style leaves a lot to be desired.