There has been as many books written on the causes of World War 1 as the war itself. There were forces at work for decades before Princip fired his shots. Was it inevitable with or without Princip? Nobody can answer that. We do know his shots lit the powder keg.
Some very good books on the origin of the war:
Dreadnought by Robert Massie
The Arming of Europe and the Making of the First World War by by David Herrmann
Europe’s Last Summer by David Fromkin
Catyclysm, The First World War as Political Tragedy by David Stevenson
Twilight of the Hapsburgs by Alan Palmer
and the standard reference, The Guns of August by Barbara Tuchman
If there is blame to be placed on any one person, the current weight of historical opinion seems to place it squarely on the shoulders of Helmuth von Moltke, Chief of the German General Staff. He was the one person determined to take a local conflict and deliberately turn it into a world war.
Thanks I'll look these up....