After his return to France, where he became a researcher at CNRS (France National Research Faculty) he investigated the developments of Islam as a social and political phenomenon there, which led to his Banlieues de l’Islam[8] (not translated) book (1987), a primer on studies of Islam in the West. He then turned to the compared study of political-religious movements in Islam, Judaism and Christianity, and published in 1991 The Revenge of God,[9] a best-selling book which was translated into 19 languages.[10]