Hmmm...this is interesting. A few weeks ago I picked up 21st Century Guide without knowing anything about Hacker or having read anything about him. I just started reading it a couple days ago. I certainly can't comment about inaccuracies, he obviously knows a lot more about pipes than I do.
And that's the problem. He comes off in his writing exactly that way. Let me say again, I had never read anything about Hacker when I started reading his book and had no preconceived notions about him. But by the time I got to page 54, I was thinking to myself, "Yes, I know how great you are and that you know everything, you don't need to tell me on every other page."
My next thought was, "I bet some of the folks on BoB have discussed this." So I came here, did a search and found this thread and the 91 replies one (and what a hell of a thread that is, I just read through the entire thing). I also read through the reviews of his books on Amazon.
I have never met him - as some here have - so I can't comment on how he is different in person than in writing; from the comments it seems that he is a great guy. I am not entirely sure why it is that his writing comes off the way that it does. He is self-promoting, certainly a necessary trait to get your books published when you are writing about a very obscure hobby, as he does. Unfortunately, I think in his case, self-promotion crosses over into...narcissism, maybe? It just feels way over the top in a "Look at me!" kind of way.
Please don't get mad at me, I don't want this to turn into the other thread.

This is just my opinion, I'm not attacking him personally, just a critique of his writing style. There must, however, be something to the way that I felt about his writing because the same sentiments have been expressed previously. This isn't to say that I am not enjoying most of his book, though, I will certainly finish reading it and I am learning a lot. I am grateful that he has been a promoter of pipe smoking for so many years and hope he continues to write and get more literature out in the public eye.