Can you have the same Europe with different people in it? The answer, says Christopher Caldwell, is no. Europe has undergone a demographic revolution it never expected. A half century of mass immigration has failed to produce anything resembling an American-style melting pot. By overestimating its need for immigrant labor and underestimating the culture-shaping potential of religion, Europe has trapped itself in a problem to which it has no obvious solution. Christopher Caldwell has been reporting on the politics and culture of Islam in Europe for more than a decade. His deeply researched and insightful new book reveals a paradox.