The first two chapters of this are fantastically inspiring. The first talks in detail about how von Neumann looked at the world, and approached problems. The second describes his unusual upbringing, and it's something I plan to reread when I'm expecting a child. Five of out five stars for this first bit.
Unfortunately, the rest of the book isn't able to keep up. Unlike Feynman, von Neumann turns out to just not have been a very interesting character. Sure, he was brilliant, but the author is quick to remind us that he (the author) isn't nearly smart enough to help you understand von Neumann. Despite this, he is clearly and unequivocally in love with von Neumann.
Often the book will meander into "von Neumann thought this. Other people said he was wrong. But they didn't actually understand what he was talking about." Like, at least five times. But the author reminds us that *he* also doesn't understand what von Neumann was talking about. So, how can he be so sure that von Neumann *wasn't wrong?* I'd be willing to let this slide once or twice with the proper citation, but none are given and the author continually apologizes for von Neumann. Genius he might have been, but never being wrong isn't a part of genius.
Along similar lines, a big chunk of this book is the history *around* von Neumann---things like the Manhattan Project and the origin of electronic computers. For the most part, von Neumann doesn't play much of a part in these histories, and in each section the author tells us "this story is better told in book X." I found myself wondering why not just read those books instead?
In all, von Neumann comes off as a Mary Sue. He can do no wrong in the author's eyes, and whenever he comes close, the author is sure to quote someone who says how lovely and brilliant Johnny was. It's boring as a historical read, and boring as a character study.
Read the first two chapters and then skip the rest.