Paul Allen is a fascinating guy, and this is his only biography. So it is worth reading. This is a well written, though a bit repetitive, short book that won't take long to read. The book retells what he has done, but without a lot of perspective.
Having finished the book, I have only partial answers to the two key questions:
1. What kind of guy is he? This is an unauthorized biography, so the author never got to know Paul Allen. The book gives plenty of anecdotes that hint at what he is like. But I still don't have a sense of who he is.
2. What has he accomplished? The book retells his life, but without perspective. It doesn't really attempt to answer the big question: If Paul Allen had simply kept his Microsoft shares, how would the technology revolution have been different? To what extent is he simply an observer, and to what extent is he a driving force?
How accurate is the book? I knew Paul back in high school (haven't seen him since) and the description of those years is fine. I can't judge the accuracy of the rest of the book, but it bothers me that the author says Paul lived off his Microsoft dividends, when in fact Microsoft has never (until very recently) issued dividends. I wonder how many other details are wrong.