"Simply not enough information." It is a common complaint for readers of the Essential Histories series that can certainly be blamed on the strict restrictions on space, but in this case especially, the statement is valid. This book gives you the bare-bones of the conflict, with very little in the way of causes for and the lead up to the war. Brief, but interesting, discussions of the most important battles, the effects on the local populace, and regional negotiations are included, but the overall result is simply incomplete. The Thirty Years' War is an incredibly complex conflict involving overwhelming numbers of players. Alliances shift, break, and reform; leaders and generals change allegiances, and the tides of war turn again and again. It is, therefore, unrealistic to expect a <100 page book to give you the kind of in depth understanding you would need to truly know and understand this war. That is not the reason I am giving this book only 3 stars.
Even considering the monumental task of summarizing the key points of the Thirty Years' War, Richard Bonney does a poor job. The primary complaint I have is a general lack of grounding. An area map is blatantly missing, so the reader will have an extremely hard time grasping the location and significance of many battles in the book as well as the basic borders and areas of occupation before, during, and after the war. It is frustrating to read about occurrences in cities and duchies of which you're not sure where they are. Without additional research to get a firm understanding of the layout of the region, much of this book will be ineffective and uninteresting. Additionally, tables summarizing the various currencies used by the key players and their respective values at the time would be an immense help, as Bonney discusses wages and contributions frequently without much grounding. Finally, a table or list of the various barons, princes, kings, emperors, cardinals, generals, and so on and who they work for would be very helpful. With only a couple of pages dedicated to quick-reference guides about some of the basic background information, this book would be much more effective.
A fun and interesting alternative history series set in Germany during the Thirty Years' War is the Assisti Shards series, starting with 1632 (don't let the silly-looking cover scare you away).
So while this book is well-written, contains some good art, gives some good history, and any 97 page book would be inadequate to describe this conflict, it still falls short of the mark set by other Essential History authors.