I will preface by noting I got into Sabbath relatively late - in the early '90s by way of Soundgarden, and have not read much about them prior to picking this up, so not sure how much of Tony's story has been previously discussed. Having said that, I thought 'Iron Man' was an entertaining look at Tony's life in and out of Sabbath. The stories of Tony's upbringing and family life were insightful into what shaped his work ethic and drive for success. The fingertip-severing story is so widely known, it was almost a waste of print to detail it once again - but on the flip side, it was a key moment in defining the Sabbath sound, so of course it must be told. From an outsider's perspective at least, it seemed like Tony delivered a fair picture of the dynamics within Sabbath - the increasing focus of creative output upon him, the deterioration of band relationships leading up to Ozzy's firing. Then the rebirth with Dio, the various iterations of the band until it basically became "Tony Iommi and Black Sabbath". Then the reunions and up to the present day. On the lighter side, the constant practical jokes, particularly the relentless torturing of Bill Ward, got me laughing many times, as well as the Spinal Tap-ish moments with the Stonehenge debacle and the "Black Sabbath with Magic Show" gig [or whatever the opening act was].
Regarding the format of the narrative - it definitely took me a couple chapters to get the rhythm. At first, I was a little disappointed by how brief each chapter was - 3-5 pages for many. I flipped ahead a little to see if things got longer as it went along - they did not. I was also a little confused once or twice, as he bounced around in time - carrying a given scenario through to its' ultimate conclusion down the road, then coming back to something else contemporary to the start, but after a bit, I came to feel like you were sitting there having a conversation with Tony, and he was reeling off stories. Given he was not setting out to write a band history, I think the relaxed, informal structure works here. He's telling his story, as he thinks of it, and the way he wants. Could I have used a little more detail about the first few albums, versus 'Tyr', of course. As a guitar player myself, would I have liked more insight into his approach to riff-writing, gear, and how he crafts his crushing tone - most definitely. But, this is Tony's chance to tell his story the way he wanted, and have to respect his wishes. Overall, I think he succeded and the book will be enjoyable for fans of Tony/Sabbath.
I will also add, given there's been some debate regarding one or more of his book signings, I attended the one at Bookends in NJ on November 1st, and everything seemed to run in a relaxed and friendly manner. His bodyguard/handler came around outside several times indicating Tony would not be signing anything other than his book, nor would he be personalizing inscriptions, nor posing for pictures [which he actually was doing]. I realize that may have been disappointing for people, but it was a book tour, not a memorabilia signing event. I was happy to get a signed copy for myself, one for a friend who was not able to attend, and a nice picture shaking hands with Tony. No complaints at all.