I own this book, and I have used some of the methods with DD (although not all) She started sleping through at about 6 months. She is a now a very good sleeper, self settles happily and wakes up happily.
The book never suggests to leave a distressed baby crying or to leave them alone to CIO.

On the Flip side...............

My sister had severe PND. She was hospitalised for near 2 months. She had this book, and became very distressed when her baby did not "conform" to what she "should" be doing. I am not totally blaming the book, but it was THIS particular book that she was trying to follow. (although there were many other factors contributing to her PND, this book did not help her at all)

The thing is that babies have their own personalities and make their own choices from birth.