How would you evaluate Hans Hesse compared to Garbe? I have the third edition of Garbe (German) and it is an amazing piece of work.
The current fourth edition of Garbe's book is an unchanged reprint of the third edition.
Hesse is superficial compared to Garbe. He also has a broader field of interest. His main work on JW is a collection of different essays on JW in the third reich. (This book is also distributed by the public affairs desk.) His is mentioned in the imprint of http://www.standhaft.org/impres.html (this shelters this private JW-site from the WTS).