The history of French collaboration with Nazi Germany during World War II is still a very sensitive subject in Gallic literary and political circles. Bestselling novelist Alexandre Jardin has learned this the hard way with the publication of "Des Gens Très Bien" (or "Very Nice People"), a startling exposé of his famous family's association with Nazism under the Vichy government of Marshal Philippe Pétain.

Mr. Jardin's new book, published in January by Grasset and available only in French, mixes the...