Cases of ex-Muslims in Europe being punished by their former fellow Muslims constitute an unacceptable practice from the standpoint of democratic societies in which human rights are respected and individuals have the freedom to choose their religion, or none at all. Ex-Muslims’ fear of punishment by their former community should prompt an open, candid, and measured discussion of the issue. Leaving Islam, Ex-Muslims and Zemiology presents the reasons for and consequences of consciously leaving Islam, based on interviews with 80 ex-Muslims currently living in Germany and Sweden. In their view, many of the practices and beliefs of Islam are harmful and unfair. Many parts of the Islamic world regard apostasy as treason or a crime. As a result, emphasis in the book is shifted from “crime” to “harm” and a thesis is put forward concerning the “decriminalization” of apostasy from the perspective of zemiology. The book highlights how a broader shift of interest in the democratic structures of Europe could allow ex-Muslims to join the discussion on the guaranteed right to religious liberties and freedom of speech in the context of the apostasy law in Islam. This should happen without fear for their own security and without facing potential suppression or social exclusion. It will appeal to scholars with interest in Islam and the conflict between religious values and an individual’s aspirations and needs.