I first read about Germaine Lubin - who loosely inspired the main character in my short novel "Isolde 1939" - in a book by Frederic Spotts called "The Shameful Peace: How French Artists and Intellectuals Survived the Nazi Occupation". I got the book in hardcover - discovered it in the now-defunct B&N at Lincoln Center, if my memory is correct - and then later bought it again in paperback because I wanted to be able to carry it around to re-read some chapters.
It is a Yale University Press book, which already tells you it's going to be overpriced ($35 for hardcover and $24 for paperback) - or perhaps it is priced exactly right, since people like me, passionate about the topic, pay the price without a second thought. But the book is a bit misplaced on the YUP list, because it reads much more like a general-audience book than a scholarly one (which I mean as a compliment, having slogged through many scholarly books whose authors wasted a great topic, with the related opportunity to connect with many readers, through their turgid prose).
I had never heard about Lubin before. The issue of the German Occupation remains a very sensitive topic in France, where I am from (I am also from Belgium and Germany, but from France most of all, and I am a French citizen) - see for instance the 2008 scandal surrounding the exhibition "Les Parisiens sous l'Occupation", showing photographs of Parisians during the Occupation in Paris - and the French have preferred to think about that period in their history as little as possible.
I remember thinking right away, when I read the few paragraphs about Lubin, that it'd make a great novel. For me it remains as important as ever to write about such individuals - not the heroes and not the monsters, but people who ended up somewhere in the middle on the white-to-black continuum of ethical (or unethical) behavior, and for whom it is still not clear whether history has been too harsh or too kind - and it may well have been too kind. It is this sort of people, nowadays, who may hesitate between looking away or taking a stand, running in the other direction or speaking up for justice, writing anonymous slander or making a difference in the world. We need to talk about them - the ones who haven't yet moved to the dark side - so that they'll recognize their dilemma when the moment of choice comes and, perhaps, they'll do what some French people didn't 70 years ago: they'll stay on the right path.