The big issue I have with the book is that I'm not altogether sure I liked the guy. He effectively re-defined the presidency, and to do that you have to have a very clear vision and the stubbornness to see it through. The thing is, while he was a populist, and I can see why Americans like him, he (to me at least) epitomises all that I find wrong about America. He pushed through a number of reforms that created greater political involvement in the population, but at a cost that ensured that future presidents only mirror popular sentiment, rather than trying to lead it.
If you want to understand the American presidency, you really need to read this book, but if you do, expect to be as infuriated as you are educated. Incidentally, if you view yourself as a "strict constructionist," read this book. If nothing else it might show you than even at the time the constitution was viewed as something that could be interpreted over time.