The term anti-Semitism was coined in the 1860s, but hatred of Jews dates back far earlier. It has radically changed its character and arguments over time. For almost two millennia the motivation was mainly religious: The Jews had rejected both Jesus Christ and Mohammed. But the phenomenon predates Christianity and Islam, and in its most murderous mutation (the Holocaust) it was racialist, not religious, in character. Jews have been attacked for assimilating, giving up their specific character, as well as for isolating themselves, most recently as a national entity -- Zionism and the state of Israel. In the 1920s and '30s Jews were attacked as a "ferment of decomposition," a dangerous revolutionary enemy of the established order, communists and worse; today they are denounced as a main pillar of capitalism, neo-conservatism, imperialism and globalism. In Gotthold Ephraim Lessing's "Nathan the Wise," whenever one of the main characters is confronted with arguments refuting the accusations against Jews, he replies "Never mind, the Jew is for burning." Lessing's play (1779) was, in fact, a rare appeal for tolerance; under the Nazis, needless to say, it could be performed in Jewish theatres only.

Before World War II, anti-Semitism was quite common, almost respectable, but Hitler and the mass murder of European Jewry gave anti-Semitism a bad name. In the early decades after 1945, there was therefore less anti-Semitism, but this closed season was not going to last. Memories faded, and so did the guilty conscience generated by the Holocaust. Genocides occurred in other parts of the world, and since the state of Israel did not always act beyond reproach, new anti-Jewish arguments appeared side by side with the old ones. If the old racialist anti-Semitism had mainly been advocated by the extreme right, the new wave of anti-Semitism was spread partly by the new left.

Whereas the old anti-Semites had made no secret of their hatred of the Jews, many of the new ones have not the courage of their conviction: They emphatically reject the charge of anti-Semitism as base calumny; they oppose Zionism, and in particular the policies of recent governments of Israel, but have nothing against Jews per se. In "A Lethal Obsession," Robert Wistrich rightly stresses that criticism of Israel does not, of course, equate with anti-Semitism. But if Israel is singled out for condemnation, and its right to exist as a state denied, how can anyone consider this as anything but (post-racialist) anti-Semitism?

Wistrich's volume is a monumental, encyclopedic survey of the new wave of anti-Semitism. It is not, as the subtitle may suggest, a history -- such works already exist. It covers Western and Eastern Europe in recent decades, the Middle East, the issues of Holocaust denial and of Jewish self-hatred. It would be difficult to think of a more competent author than Wistrich, head of a Jerusalem research institute, who has given decades to the study of the subject and has a good knowledge of recent European history and languages, and particularly of Nazism. At a time when anti-Semitism is again becoming fashionable in European societies, not to mention the threats by certain Muslim leaders such as Iran's president Mahmoud Ahmadinejad, this work needs no special recommendation.

It has certain weaknesses, perhaps unavoidable. Being exposed to massive dosages of anti-Semitic literature, with its mad conspiracy theories and its denial of the obvious, makes it exceedingly difficult to retain the almost clinical detachment needed to understand and explain anti-Semitism. At times this work is unnecessarily polemical in tone.

Wistrich's facts are all true, but do they present the whole picture? If so many speeches critical of the Jews and Israel have been made in Germany recently, how to explain (a reader may well ask) the fourfold increase in the number of Jews living in Germany during the last 20 years? How to explain that despite the rise of virulent anti-Semitism in France, many Jews play leading roles in politics and public life? Even Russia had two prime ministers of Jewish origin in recent years. While angrily denouncing Jewish self-hatred, does not the author on occasion misinterpret the line between self-hatred and self-criticism? Even the early Zionists come under fire for their "negation of the diaspora" and the dim view they took of the miserable Jewish existence in the East European shtetl.

This is a deeply pessimistic book, all too understandable in the light of the Holocaust and the age of weapons of mass destruction. However, knowledge of the dangers is one thing; a pessimism leading to fatalism ("all the world being against us"), as if there were little or nothing that could be done by the Jews and Israel to avert a disaster, is not a guide for survival.

Walter Laqueur is a distinguished scholar at the Center for Strategic and International Studies and author of "A History of Zionism" and "The Changing Face of Anti-Semitism."