I've read, among others, Eric Kaufman's Prospect article "Breeding for God", Rose-Anne Clermont's Der Spiegel article "On Becoming Un-German", and David Aaronovitch's essay "A Proper British veil-wearer" in The Times. All of them make interesting points about demographic change, but I'm unconvinced by some of the claims of the first two articles (Catholics didn't outbreed and so dominate freethinkers in France over the past two centuries, and German Turks' TFR is also at sub-replacement levels, if significantly higher ones). The third article explores what seems to me a vaguely plausible second- or third-order consequence of these misunderstandings.
[T]here is an alternative that we are sizing up right now: we could march on towards a clash of civilisations, a Kulturkampf. But we won’t like it. "Wollt ihr den totalen Krieg?" asked Goebbels. "Ja!”"they replied. "Nun," said Goebbels, "Volk, steh auf und Sturm brich los!" (Now, Nation, arise and let the storm break loose!) And it did.