I came across this book a few days ago now, and before I begin, I'd like to stress how utterly hopeless I was at drawing manga before now. I've read it for years and always longed to draw something that looks even vaguely like actual manga, like it's supposed to. I never had.
However, this book is nothing short of miraculous. The instructions are so clear and so easy. There are a lot of examples of how to draw right, but even more usefully, there are examples of what happens when you do it wrong. If your drawing turns out to be not what you expected, it's so easy to pinpoint where you've gone wrong. With this book, you'll learn from your mistakes and get better as an artist, rather than slump at the same level of "not quite right-ness".
This book has done more for me in a few days than several years of struggling with other books. I'm now looking for other books in the series.
If you're serious about manga, if you're frustrated and not sure why things aren't turning out like they should, you need this book. Please, please consider buying it because it's helped me enormously.