I just picked up this book by Edgar Kruyning who is a 5. dan in Judo, 5. dan in Yoseikan Budo, 5. dan in Yoseikan Aikido, and has studied Tenshin Shoden Katori Shinto Ryu in Japan.

The book overall looks very good and professional.

There is a brief foreword by Mochizuki Hiroo, a chapter on the history of Yoseikan (wich mentions Kano, Ueshiba and Funakoshi) and a good biography of the author.

The technique part is divided into a Judo part, a Kata part (which covers unarmed techniques, Iaijutsu and a couple of weapon defenses), and the main part of the book covering Tenshin Shoden Katori Shinto Ryu.
The book contains 1000+ photos, and would be invaluable as a memory aid. It is not possible to learn techniques from this book as there are gaps in the photo sequences (which is a good thing if you ask me).

My background is Judo, and I have seen some Yoseikan Aikido, and these parts look very good to me. I am not qualified to comment on the quality of the TSKSR techniques.

One possible drawback is that the book is in Dutch, and I am not sure if it has been translated into English.

Overall I would give this book 5 out of 5.

It can be purchased through www.yoseikan.nl or sportboek.nl