Would it be accurate to say your most consistent theme throughout The Low Countries is the effect of the Christian religion on Dutch culture, politics, and life?
The short answer is "not consciously". The central line or chain of thought that helped me get through writing the book was the internationalism of the Low Countries, their position as (North-)Western Europe's "crossroads, cockpit and marketplace", their openness to outside influences and their influences on other places. From the mix of "Northern" and "Western" archaeological finds in the Drenthe dolmens, to hosting the EU and NATO institutions, the International Court of Justice, and the International Criminal Court.
In my own mind, one of the worst distortions of this approach is that I fail to bring out with concrete examples just how provincial and parochial a lot of life and thought in the Low Countries is and has been (I do make a couple of bald references to provincial particularisms, but give no memorable specimens).
One thing that I did want to do, very consciously, was not be limited by subdsciplinary divisions into "Political History", "Social History", "Church History", etc., and I suppose Church History, partly because of my own (non-specialist) interests, is one of the main beneficiaries of that. I treat, briefly, sports, tourism, food, education, and all sorts of other issues that the standard overview leaves out (or at least, tended to leave out when I was cribbing from them 20 years ago - perhaps I'm just doing what everybody else does these days, without realising how permeated I am by the "spirit of the age").
The extensive coverage of Christianity in various forms (still, given the constraints, insufficient: the Mennonites don't get the coverage they deserve, let alone a lot of the smaller Protestant groups) is due solely to the historical importance of Christianity for most of the history of the Low Countries. From the 7th century to the 1970s, it's impossible to write about how people conceived of their world, their society, their duties and their hopes without writing about some variety or other of Christianity, or some sort of conscious reaction against it.
And thanks for this spur to reflecting on my own writing processes!