An erotic novel written under a pseudonym might normally struggle to find a mainstream publisher and a wide readership. Not so, it seems, when it is penned by a Muslim woman living in a traditional Arab society. “The Almond,” a semi-autobiographical exploration of sexual freedom, has sold 50,000 copies in France since Éditions Plon brought it out here last year. And it has now appeared in eight other languages, including English. With its explicit descriptions of lovemaking, the book has been compared to Marguerite Duras’s coming-of-age novel, “The Lover,” and to Catherine Millet’s more recent confessional essay, “The Sexual Life of Catherine M.” Yet in this case the feisty 40-something North African author who goes by the name of Nedjma appears to have been motivated by more than a desire to titillate.