""Revolutions, like trees, must be judged by their fruit," Ignazio Silone wrote, and this is the standard the authors apply to the Communist experience - in the China of "the Great Helmsman," Kim Il Sung's Korea, Vietnam under "Uncle Ho" and Cuba under Castro, Ethiopia under Mengistu, Angola under Neto, and Afghanistan under Najibullah. The authors, all distinguished scholars based in Europe, document Communist crimes against humanity, but also crimes...