The official Nikon user guide for the D90 explains where menu items are and what they do. It doesn't expand on them much or give you any "experienced user" hints.
Being a keen photographer, and having had a D70 for a number of years, I thought I'd better off get an advanced book to really help me master all the new features of the D90.
Unfortunately, this book is really aimed at beginners, as it spends a lot of time explaining simple concepts like the different ASPM modes. Where the author does express his personal opinion on settings to use, he's generally talking from his style of photography - somewhat limiting the use of this book.
I was rather hoping for a book that helped me master the D90. This book, although good, should have been titled "Getting Acquainted with the D90". It's a bit like the user guide, but explained more thoroughly.
If you're new to photography, haven't had a DSLR before, or are just moving over to Nikon from Canon for example, this book would be well worth the maximum 5 stars. If you've had a Nikon before and are the "Prosumer" the D90 is really aimed at, you may be better looking elsewhere. And if you do, please let me know if you find a book that does what it says on the front! :-)