Short Review: This was fascinating, detail, occasionally boring and still left me wanting more with some areas. I spend five months slowly working through this. There is about 450 pages of main content, which did feel both too long and not long enough. There is so much that could be written. But in an overview, you cannot talk about everything.
What is most helpful is that Amar uses history, comparative legal analysis (with state constitutions, English common law and notes from drafts), legal history from court cases and political science analysis of what was possible to have been based based on political realities on the ground. This is more than just an analysis of what is in the constitution. That is here as well, but the parts around what is in the constitution is helpful to give context to the actual content.
I think the best sections are the sections on the role and politics of slavery. That analysis is was very helpful to understanding not only the sections on 3/5 clause but the politics around other compromises that were impacted by slavery.
It is a bit dry in places. But I am not sure that large sections of the book, could have been cut without harming the larger flow. I did think as I was reading it that it could have been re-organized in places. There was a fair amount of repetition that could have been cut. But most of those repetitive sections made sense if someone was trying to read different areas of the constitution instead of reading the book as a whole straight through.
My full review is on my blog at http://bookwi.se/americas-constitution/