Now, he's got a book out about the origins of the First World War, called CATASTROPHE. You'd think this ground had been pretty thoroughly plowed, but Hastings revisits an earlier argument, that Germany was the primary belligerent, and is most at fault for starting the war.
This is the case Barbara Tuchman makes in THE GUNS OF AUGUST, still the most influential history of events, and her view is backed up by Sir John Keegan and Paul Fussell, among others, but it wasn't always so.
Winston Churchill always held Germany responsible, as did a number of his contemporaries, John Buchan, for one. (Churchill is in fact known to think that both wars were continuous, and that the years from 1918 to 1939 were no more than a static interlude of false hope.) This is why Woodrow Wilson had such a tough sell at Versailles, because Clemenceau and the Brits insisted that the Germans accept full blame, and pay crippling reparations. The humiliation of the peace, and the collapse of the German economy, almost certainly led to Weimar's paralysis, and the rise of Hitler.
After the June, 1914, assassination of the Archduke Franz Ferdinand, by a Bosnian nationalist, London had every reason to believe Berlin would exploit the Balkan crisis. Leaving aside the fact that Austria-Hungary had its own internal tensions, Germany did indeed turn the situation to their advantage. Their intention, if they could persuade France to remain neutral, was to attack Russia, but avoid a war on two fronts.
In the event, when Germany invaded Belgium that August, beginning their offensive in the West, to eliminate the French threat, everybody's calculations went off the rails. You have to look at the chronology of mobilization, which is complicated, and then decide whether Germany was bluffing, or trying to buy the pot, without in fact going to war, but it seems to me Hastings has got it right. The actions of the British, the French, and the Russians were taken in reaction to German saber-rattling. A general European war might never have happened, if Germany had shown any interest in conciliation, but their air was to dismantle British hegemony, and establish a German one, in central Europe, annexing Poland, and across their colonial empire, particularly in central Africa. The result, in a word, was catastrophe, for all involved.