Substantive, colorful and interesting for any student of WWI, Diplomatic History or broader International Relations.
Each third has something unique to contribute. While many liked the final third of the book, I really enjoyed the deep-dive into the Austrian-Serbian dynamic that occupied the first. The second, while undoubtedly the most dense and complex, can be a fun intellectual excercise to read through an IR theory lens. Some totally new central arguments, such as British threat perceptions and subsequent appeasement of Russia as the basis of the Anglo-Russian alliance also added a great deal of depth and clarity.

However, would not recommend as an introduction to WWI. Reading some other general war history (Keegan's, Stevenson's) first would add immensely.