This book methodically and thoroughly delivers exactly what it promises. And this English-language book is a rare treasure, because there are very few books which cover this subject in English.
Starting from the pinnacle of the entire German war machine with the Kaiser himself, the book details the command structure, unit responsibilities, and specific composition for the entire imperial German army. Following through its top-down progression it covers: the Supreme Army Command, the War Ministry, Supreme Commander East, the army groups, the armies, the general (corps) commands, and the divisions. The book also unravels numerous mysteries, such as the bewildering array of unit naming conventions, the creation and dissolution of temporary commands, the large array of unit types, the varying armament compositions between unit types, the growth of the air force, and all the administrative and logistical elements which are essential to any modern armies battlefield success. In addition, it presents several appendices which list: the complete German order-of-battle (OOB) for August 1914, the 18th Army's OOB for the March 1918 Kaiserschlacht Offensive, a summary list of brigade and mobile unit formations throughout the war, and a listing of all the army and higher level unit commanders throughout the war.
The book tackles a very daunting subject and quite lucidly explains the inner workings of the German war machine. If you want to know how the German army was structured during the First World War, then this is the book for you. The book suffers from a few weaknesses (but its valuable content overrides these). The most annoying thing about the book are the incorrect dates found throughout the first part of the book (e.g. p. 79 "During the 1918 offensive, General of Cavalry von der Marwitz was in command. The 2nd Army was dissolved on 13 January 1918 in Gembloux."). I actually sent an email to the publisher months ago about this but still have yet to receive a response. The other significant complaint I have is that the writing style is very dry and dull, but it is a reference work after all.
In summary, I recommend you buy this book if you are doing scholarly research on the WWI German army. If you are looking for a narrative history or the complete German orders-of-battle for all the individual battles during the war, then look elsewhere. All in all, this is an outstanding and rare English-language reference work on the WWI German army.