Cataclysm: The First World War as Political Tragedy, by David Stevenson.

2004 Basic Books ISBN 0-465-08184-3

Stevenson is one of the leading scholars on WW I, and this book is well worth reading. He makes use of previously undisclosed records from governments not only in Europe but globally. It is complex reading, involving all the secret treaties and internal politics of all the major players. You'll have a different view of the decisions made on all sides; it was far from a series of 'political accidents', and this was true of decisions made on all sides during the war as well. It's a must read, and an excellent reference work. WW I was the most important war of the last century, and yet it is the least known by most people these days; WW II was merely a sequel to this era of geopolitical maneuvering.