Different countries find different things appealing. Adultery for Beginners was lapped up by the Spanish, who produced three different versions -hardback, paperpack and a smaller hardback edition especially for newstands - but they haven't taken any of my other books, whereas the Germans spurned Adultery for Beginners, but liked Nice Girls Do and the rest. The same happened with the audio rights, although I did finally sell the Adultery for Beginners audio rights and they came out this summer, ages after all my later books had made it into the spoken word.
Then there's rewriting. The Americans wanted the sex toned down in Adultery for Beginners. The Dutch wanted more sex in Nice Girls Do. The French just wanted everything shorter. Adultery for Beginners sold to about ten countries almost immediately and only one - Norway - renamed it, whereas Nice Girls Do became Under Blue Skies in all the European countries it sold to, though stayed the same elsewhere.
It's really difficult to have a genuine international best seller. There are plenty of examples of authors who are huge in one country never making it elsewhere. Nora Roberts, who the Washington Post described as the most successful novelist on Planet Earth, every now and then gets a push over here, but her books don't seem to 'take' among us Brits. Rosamunde Pilcher is a bestseller here, but way beyond that in Germany - I met a man last year whose sole employment for the past 10 years had been working with German films crews who were in the UK to film RP short stories.
So where does that leave a writer? Back where they've always been. You can't write for anyone but yourself. You can only write the book that comes from your heart. If you're lucky it will appeal to an outside audience, if you're very lucky it will appeal to an international one. But you can't force it. Just be happy if it happens.