It all depends on what you consider heavy metal music, and if you even think there's any heavy metal around anymore. Two books in the bookstores at the moment take quite different views of what constitutes metal, and which one you prefer will depend on how you define the genre. (Which makes me wonder what people with no prior exposure to metal will think -- too bad I can't think of any friends of mine who have lived under a rock that long.)David Konow's Bang Your Head: The Rise and Fall of Heavy Metal and Ian Christe's Sound of the Beast: The Complete Headbanging History of Heavy Metal start out in the same place: Black Sabbath as the progenitors of metal, with some help from Led Zeppelin and Deep Purple. But Konow takes a much broader view of metal -- his 1970s include a lot more Kiss and Aerosmith than Christe's; his 1980s focus much more on bands that got MTV play during the daylight hours as well as the Headbanger's Ball on Saturday nights, while Christe prefers the bands most people only knew from reading the black t-shirts of their high school's headbanger clique. So Bang Your Head deals with the end of the most high-profile days of glam metal, while in many ways the relatively underground scene Christe chronicles had nothing to lose from changing fashions and the grunge explosion.
For me, Bang Your Head was a lot more fun to read -- it tells the amusing stories of the bands' attempts to life the wildest rockstar lives possible. One of the Amazon reviews calls it a "puff piece" for this reason, but seeing the details of the bands' lives is what many fans like (hence the popularity of such shoes as MTV's "Cribs" where the camera tours famous people's houses, and of course "The Osbournes" which enthralls people who never bought an Ozzy Osbourne album in their lives). Sound of the Beast loves to categorize -- power metal, death metal, nu metal, etc. -- and for those with eclectic tastes like me, putting everything into its own little box gets annoying pretty quickly. "OK, I own three out of ten albums on his list of definitive '70s progenitors, but only one of the list of paradigmatic New Wave of British Heavy Metal bands" -- well, the list titles aren't really so pompous, but they still made me feel like I was supposed to measure up to his standards or be considered a "poser." Remembering the comment in Chuck Klosterman's metal-fan memoir Fargo Rock City: A Heavy Metal Odyssey in Rural North Dakota about the surprising popularity of certain non-metal artists, like the B-52's, among his head-banging friends, I'm sure I can't be alone in wanting to ignore the habit of sticking a label on every group (then and now).
Metal music is escape -- the kind of escape you prefer is up to you. If you want to escape fluff and find something that holds up to even some non-fans' critical analysis, you'll probably prefer Sound of the Beast. If you want some energetic fun, you'd do better with Bang Your Head. However, if you just want to know about the evolution of the music that has held so many people (and particularly disenchanted young people, and those who remember being one) in thrall for decades, you might want to set aside the time to look through both.