Sometimes you have the experience of reading an attack on your views and find that this attack gives an accurate account of what you believe, so that you say "Yes, that is where I'm coming from" and understand things about your own beliefs better than you did before.
This book is an example of that.
It was published in 1915 and made the argument that the war was in fact a Glaubenskrieg, a war of values, between the individualist, materialistic individualism of the British (and to a lesser extent the French) and the stern, collectivist, martial values of the Germans.
It's a rant against liberalism from the standpoint of a completely different way of looking at the world. As such it helps to a better understanding of the essential values of liberalism.
It is worth adding that this view was not of course the only one found in Germany at the time and also that this way of thinking, opposing the values of militarism and a particular vision of the heroic to those of liberal mercantile civilisation, was found in the Entente countries as well, in the thinking of people as varied in other ways as Patrick Pearse, T. E. Hulme, and Charles Maurras.