I waited till I had read the book (at least, partly), and I would say this is a good book.

Do I have suggestions/comments to improve it? Certainly! But then regardless of the existing perfection level, any book can be taken to new heights. (Personally speaking, I'd love to get more feedback on how to improve the LMMS User Manual.)

The authors' approaches vary, and any reader has to browse the book first to verify whether it fits his style, and current needs. But that cannot be sufficient ground to call it trash.

In general, Packt publishes many good books, at par with books from the other publishers.

As regards the business tactics, I guess Packt contacts competent people who can write or review books based on their contribution in a project. While self-publication business like Lulu facilitate people with creative urge, Packt makes active effort to draw out and encourage such people. Personally I find Packt's approach more positive, despite the obvious risks.

The first Harry Potter book was rejected by 12 publishers, none of who had gone to seek her work. Contrast that with Packt's approach.

In the end, who will spawn new exciting writers, at his own risk?