The answer, of course, is that no single country can be blamed for a catastrophe as large as World War I. This argument is made at length by Christopher Clark's The Sleepwalkers, which some in the international relations community consider to be the new standard account of the causes of WWI.
Clark starts with a structural approach to WWI, and adds to it with (I think) an excellent understanding of how flawed and sometimes irrational leaders (Wilhelm and Nicholas don't come off well here) led to bureaucratic mis-function and bad organizational decision making:
[Clark] concedes the importance of basic structural causes, such as
rigid alliance commitments; the temptations of preventive war on a
rapidly growing, militarized continent; and the peculiarities of
authoritarian decision-making. Yet he believes that such forces alone
cannot explain the war and might just as likely have led to peace. He
argues that war emerged from a complex conjunction of factors, each of
which was far from inevitable and in many cases even improbable, often
because it involved decision-makers who behaved less than fully
rationally. They indulged in illusions of power, stereotypes about
their enemies, and outmoded conceptions of sovereignty; they succumbed
to the demands of transient domestic coalitions; and they misperceived
their surroundings, sometimes for no good reason. In all of this, such
leaders were sleepwalkers, generally unaware of the horrific
consequences of the war they were about to unleash. (source)
How much blame does Clark put on Germany?
[Clark puts] a stake through the heart of a common narrative that has Germany mobilizing first so as to spring the preventive war its
generals had long advocated. It didn’t. Clark documents how Berlin’s
political and military leaders stuck to their blithe belief that any
conflict could be localized. Russia’s mobilization, he says, was “one
of the most momentous decisions of the July crisis. This was the first
of the general mobilizations.” (source)
There is plenty of blame to go around in Clark's account, much landing on key figures in Russia, Serbia, France, and England as well as Germany and Austria-Hungary. Perhaps the most tragic aspect of Clark's work is he concludes that the war was not inevitable--and by implication, neither was WWII, the Holocaust, Hiroshima and Nagasaki, and so on with the litany of 20th century horrors.
An aside: if you follow the NYT link, you'll see mention that Tuchman in Guns of August misdated Russia's mobilization as two days later than it actually occurred.