Review of the hardback: 'The existence of extremism seems to contradict the idea that participation to political activities is guided by the rational choices of the individuals. This book shows that this is not the case. Extremism may be explained as a rational reaction of the individuals when they face some circumstances such as a 'social hole' in thrust between groups and some asymmetry in the distribution of political rents. The original and challenging contributions of this book were conceived with some unintended foresight. Their publication occurs at a time when, once again, a numerous movement of young people faces the choice among more and less extremist policies. Both the members of the anti-globalization movement and the policy makers who want to avoid it taking an extremist direction may benefit from reading this book. Its insights elucidate the specific circumstances under which extremist, but somehow rational, choices may arise.' Ugo Pagano, University of Siena