His WWI book was awful. It's entire premise is anachronistic, and it shows the same predilection for snide ad hominem attacks as the rest of his writing.
I beg to differ. I thought that Ferguson"s World War One book was pretty good. It suffered to a small degree from AJP Taylor disease, but a very mild case only--you learn a lot from TPoW http://amzn.to/2gnp2em, while you learn nothing—in fact, your Δ(knowledge) < 0—from Tayllor's Origins of WWII http://amzn.to/2gnp2em.
My main criticism is that it does not make its central thesis clear. The central thesis is that British intervention in World War I was an absolute trainwreck clusterf%#+ because Britain was strong enough to prevent an early German victory yet not strong enough to impose an early Allied one, and an early German victory would have led to a Europe much like the one we have now while avoiding all the 1919-89 unpleasantness.
Now do note this: While I think Ferguson's book is interesting, I do think that Ferguson's central thesis is probably wrong.
The Europe we have now is one that is dominated by a large German-speaking Palatinate.
The Europe in Ferguson's counterfactual scenario would have been one dominated by a large German-speaking Prussia.
There is a huge difference.
And I think Ferguson's harsh judgments of British policymaking in 1914 are wrong as well: The British played the game of nation according to the rules of the time. They had very good reason to assume that Germany was weaker and Russia stronger than turned out to be the case. Thus they had reasonable and rational confidence in a rapid victory. And the German High Seas Fleet was a true existential threat.
But it is very clear to me that TPOW http://amzn.to/2gnp2em is a useful and valuable contribution discourse about political military economic affairs—in a way, alas!, that many of Ferguson's current ravings are not.