I'd read similar comments about "Mustang Performance Handbook 2" by Mathis being
heavily decontented by HPBooks editors. Supposedly, it had something to do with bookshelf space and marketing BS.
There was some thread on http://www.corner-carvers.com/forums/ about it, IIRC.
Corky Bell may be a swell guy but Max Boost didn't give him much opportunity to
share his knowledge beyond the beginner stage. That's a pity.
You know how some engineers can design insanely complicated devices - but others come up with a simple, elegant way to do the same thing? Corky's one of the former. And he'll prove anything with math, even if practice doesn't actually hold up. Keep that in mind while reading his friendly Smith-esque prose. I'd use this book to get a handle on the basics of what everything and what it does, but reach for something more advanced when doing actual design.
Never written for HP, but I did do content edit on the book by Jay Miller that they published. Basically just a run through by someone with a bit of knowledge to ask clarifying questions. Let me tell you, that one is not dumbed down on little bit. Need to know how to do a rebuild on your turbo? Step by step, including failure analysis.
Books are written for a market. That's the job of the editor. None of mine have ever been trimmed, although I am usually given a page target because printing works best in certain page multiples. My editor did improve the Locost one considerably with a couple of well-timed questions.
My experience with HP Books is that I did have a glossary cut from the book for page count considerations, but it wasn't decontented otherwise.