Joseph Berger, who covers the religion and neighborhood beats for The New York Times, gives us a glimpse into the world of contemporary Hasidism and explains why a group that logically should not exist anymore is thriving.

Indeed, Hasidism in North Amer-ica is mushrooming. In Brooklyn, Los Angeles, Baltimore, Milwaukee, Minneapolis, Montreal and Toronto and in many other cities a rebirth is taking place. To cite just one incredible example: At the end of World War II, there were only about 300 Bobover Hasidim in the world. Today, there are 50,000 in Borough Park, Brooklyn, alone.

The number of Hasidim in the United States doubles every 20 years. Their population in New York is now estimated at 330,000, which makes them 30 percent of the city’s Jews.

And, most astonishing of all, New York’s Satmar have more children in their schools than all the non-Orthodox Jews in the city have in their schools combined.

What makes Hasidism prosper is the groups’ incredible birthrate. Berger writes about one woman who lost two children in the Holocaust and started life again in America; by the time she died she had more than 200 grandchildren and great-grandchildren.

Nowhere else in America is there such a passionate commitment to study Torah, and yet many native-born Hasidim speak English as if they were recent immigrants. Nowhere else in America is there such a low crime rate, and yet there is a suspicion of the government and a reluctance to report criminals to the authorities. Nowhere else in America is marriage and family life held in such high esteem, and yet nowhere else is there so little preparation for marriage. Nowhere else in America are there so many agencies that help the poor and the sick, but there are also Modesty Patrols that enforce the community’s moral codes on everyone.

Berger tries to be fair and objective. He describes both the virtues and the faults of the Hasidic world.

The Hasidic work ethic, he writes, is focused not on greed or on material success but on being able to support one’s family and do good in the community. But he also describes the sexual abuse that occurs in communities that have such strict separation of the genders.

“In 2009,” Berger writes, “Justice Gustin Reich-bach of the New York State Supreme Court in Brooklyn publicly admonished the Hasidic community at the sentencing of Yona Weinberg for molesting two boys who were under 14 years old.

“‘While the crimes the defendant stands convicted of are bad enough, what is even more troubling to the court is a communal attitude that seems to impose greater opprobrium on the victims than the perpetrator, he said.’”

He explains the ambivalence toward government as a carryover from the European world, where the government was hostile to the Jews, who had to learn how to outwit the government to survive.

The book is a bit too long. The gory details of the fight for control between the Satmar followers of two brothers who struggled to inherit their father’s position could have been shortened or deleted (the chapter’s title is “Cain and Abel in Brooklyn”).

And there should have been some explanation of why Chabad alone reaches out to recruit among other Jews while other Hasidic groups are content to live among themselves. A discussion of the worldview that is at the heart of Hasidism would also have been informative.

The most striking point that Ber-ger makes is the contrast between the value system of modern America, which is based on autonomy, material success and the pursuit of pleasure, and the value system of these groups that believe in the authority of tradition, in self-restraint and in the sanctification of the everyday.

Whether we agree with Hasidism or not, it behooves us to know more about these fast-growing communities that are transforming the demography of American Jewry. Berger’s book is a helpful guide to a world that was once dominant in Jewish life and is on the rise again.