The book "tells the story of Batman" (the phenomenon, not only the figure) and with the help of that, and importantly, provides a cultural historical study of fandom, or nerd culture. In the case of this book, by nerd is understood a personality very, very close to that of the Comic book guy in the Simpsons, and not a computer geek.
It becomes quite evident that while the authors and publishers of Batman (like any other such comic and later movie franchise) have always been very responsive to changes in the surrounding societal and cultural environment (driven by the profit motive, of course), the increasing adoption of the Internet has made fans -- and also the more general audience -- an increasingly influential stakeholder in movie and comic production even to the degree of movie scripts being altered during shooting in reaction to discussion forum outrages.
Was it good?
While I'm not a Batman or comics fan by any means, the book works very well at both levels: in telling the Batman story (how the figure and the stories have reacted to changes in cultural "mood", thereby reflecting societal conditions) and especially discussing the "history and increasing prominence of the nerd".
The book is quite significantly tilted towards covering the history of Batman, but regular short and reflective discussions about "what this tells us in cultural terms" well justify the ample Batman content, and make the book actually come across quite balanced.
The main take-away for me?
While it should not have been as a revelation, it still quite astounded me to realise how overly engineered comic book characters, comics and movies are. Namely, even some of the very fundamentals in a character's "origin story" can be readily abandoned in the interest of sales. For example, the early Batman, to my surprise, even engaged in time travel and battles in parallel universes...
Who should read the book?
Quite obviously the book is very likely to appeal to any Batman or superhero fan, or a proud (or insecure) nerd. However, I think that the book should also be ready by anyone who perceives superheroes or comics or movies featuring them childish, non-serious and/or a waste of time.
All in all, I really enjoyed the book and can quite readily recommend it -- also as study in cultural criticism.
The book on Amazon.com: The caped crusade