I love japanese food, and Hideo Dekura is certainly one of my favorite author on this topic. This book is an excellent survey of all Japanese food-related topics, such as a dozen pages on kitchen knives, pretty much all common ingredients or utensils, etc. It's also full with recipes (I'd say easily over 100), half of which are the "classics" you can find in other books on the topic (tempura, miso soup, ramen, sushi, etc.), and quite a lot are recipes unknown to me (by the author I assume and they look tasty, but maybe not what you'd expect in an general encyclopedia).
So it's half a cook-book, half a reference book on common ingredients. If you own already some good japanese cookbooks, half of this book will be redundant (I guess all aficionados know what wasabi or daikon is) and you'll end up with a recipe book you have to sort through (not many recipes have pictures of, so you really need a high threshold of motivation to cook some - which I didn't reach...).
In the end, this book will not be really useful for an amateur wanting an intro to japanese cuisine. If you're an academic looking to grab every information you can get on topic, this book will give you some to chew on. If you're a beginner or intermediate looking for some great recipes then rather get his other book (Contemporary Japanese Cuisine: Classic Recipes, Fresh Flavors), or if you're looking for a serious japanese cookbook, then get the real deal: Japanese Cooking: A Simple Art!
The other major problem I really had with this book is really the size/weight. Pages are pretty thick and heavy (almost 600!) like a book for kids which makes it pretty impractical (you really don't want to read this on your morning commute). The typography is not pretty, quite confusing and printed text is really big (size 14 points, double spaced lines, etc.). A more professional and informed page layout would have made the book much more inviting to be read, and especially two times lighter.
So nothing wrong with the content, really, but there's lots of basic material that you certainly already have if you possess already a few japanese cookbooks, which makes this book marginally useful, so you might end up using it less than you'd like unless your phd thesis on japanese cooking is due next month or looking for some original recipes you've never seen somewhere else (or you just compulsively need to buy every japanese cookbook ever printed - which is unfortunately my case...).