Bugs in software are a lot like bugs in the home. Even though you know they're there, sometimes you just don't want to know. As a tester, of course, finding bugs is part of what we do. If I were to continue the analogy, I guess if an exterminator had an assistant who's job was to walk around a house and say "there are bugs right here - spray your chemicals here!", that's sort of what testers do.
It's a different perspective sometimes from the other side. If I pride myself on a clean house, I don't want to be told I have bugs - same thing if I've created something like a software program (or a book)...but inside, I somehow know that I really do want to know about the bugs.
The point that I'm happy to get to by only the third paragraph is that the other authors of hwtsam and I, have, for better or worse, started tracking a list of bugs in the book. We know of at least 3 already, and there are bound to be more. In another week or two, I think I'll publish the list somewhere on hwtsam.com. If you find a bug we don't know about, maybe we'll send you something (or maybe not, I'm still thinking about what would be appropriate - and affordable).