After reading Shoninki, released by the same author, I decided to go further, and get this book. It was not a mistake. I must say this book is written much more scholarly, than the Shoninki translation, due to a greater number of footnotes. I realize, mr. Cummins wanted both books to be written in such a way, but the publisher insisted that the Shoninki translation be made more "readable". Anyway, I really like the way this one turned out. The large format is very practical, and readable.
As for the material in the book itself; this edition contains three books: the Ninpiden itself, the 100 Ninja poems, and three Gunpo Jiyoshu scrolls. While most people would probably buy this just for the Ninpiden, I must say, the other two books inside, are not in the least less valuable or informative than Ninpiden itself is. Though, as a big fan of Shoninki, I must say I miss some of the more philosophical and esoteric material included in Shoninki; these books are very practical, and concentrate on tools and methods of physical infiltration instead, though there are sections devoted to communication skills and espionage. So whoever gets this book, I advise you get Shoninki with it (and Bansenshzkai when it comes out though I haven't read it myself). If you are in any way interested in the shinobi arts, be sure to get this book, and other translations by the same author (there is more on the way). I believe them to be the most reliable (though not without flaws) translations of these old shinobi texts out there currently.