BOOK REVIEW / NONFICTION : In Defense of Immigrants’ Contributions to America : FRESH BLOOD: The New American Immigrants <i> By Sanford J. Ungar</i> ; Simon & Schuster $25, 399 pages

Here is a book that every American interested in immigration will profit from reading.

Sanford Ungar, the son of Jewish immigrants from Cen/ Eastern Europe, has spent several years looking as a reporter into the wave of immigrants entering the United States from all over the world. Some politicians, notably Gov. Pete Wilson, are railing against immigration, as if it would destroy the country. Ungar robustly finds it, on the whole, good for us.

Ungar portrays the modern immigrants with sympathy, yet with unsentimental accuracy.

At the center of Ungar’s presentation is his belief that America is still a nation of immigrants and always will be.

“To be American,� he says bluntly, “means being part of an evermore heterogenous people and participating in a constant redefinition of a complex, evolving social fabric.�

He recounts in his prologue the effect on him of his own return to Tusice, now in Slovakia, the village where his father was born.

�. . . I know now, really, where my father was from. . . . I was no less American than ever before, of course, but now, in middle age, I had discovered my own immigrant consciousness. Indeed, in that sense, I could now feel even more authentically American.�

Ungar, once a reporter for the Washington Post and now dean of the school of communications at American University, quotes sermons and speeches of 100 years ago raising alarms about the harmful impact of poor immigrants on the American economy and the American political system. He points out the obvious, that this is “a wealthy country built by immigrants.�

He quotes liberally from his interviews with opponents of immigration, such as former Gov. Richard Lamm of Colorado and the Rev. Timothy McDonald, pastor of a Baptist Church in an African American section of Atlanta. Both, like others, deplore the economic competition from immigrants.

Ungar acknowledges that exploitable Latinos are willing to work for wages that, while low for Americans, are high by Mexican standards.

“But one study after another,� he writes, “has shown that overall, immigrants still have a positive economic impact.�

He says that “in a flashback to the old quota days, the ‘real’ Americans have their distinct preferences among the newcomers. Surveys reveal that virtually all Europeans--even the nationalities once discriminated against, like the Irish, Jews, Italians and Poles--seem to have achieved relative acceptance as equals at last. Now it is the Latinos--and Mexicans in particular, a category that for many people often includes undifferentiated Central Americans--who are most disliked, with Asians (especially Koreans and Vietnamese) close behind. Clearly, the longer a group has been in the United States, the more likely it is to win approval; therein should lie a lesson.�

The bulk of this book is based on interviews Ungar did with immigrants around the country.

Ungar recognizes that “the current system of controlling and regulating immigration clearly does not work, and therefore is easily--almost universally--mocked and defied. He offers “a few modest recommendations:�

* Raise the number of legally admitted immigrants to more closely approximate the number who actually come. At the Mexican border in particular, allow Mexicans and Central Americans to come and go legally as the demand for their labor fluctuates.

* Law enforcement at the border should focus less on illegal people than on the drugs and diseases those people may be carrying.

* Reform the Immigration and Naturalization Service--Ungar calls it “one of the worst performing and least effective parts of the federal bureaucracy�--and reduce its size.

* It is reasonable for the federal government to help the states pay for any economic burdens imposed by unexpected immigration flows. But Proposition 187 and similar proposals are “potentially dangerous for the nation� because they would deter Latino Americans from seeking services they are entitled to, kick the children of illegal immigrants out of school to get an “American� education on the street and, by denying medical care to many, increase disease and risk to public health.

Part of Ungar’s first suggestion, to let the law of supply and demand largely govern the flow of people back and forth across the Mexican border, might win the support of market-oriented business people. And surely enforcing the more onerous parts of Proposition 187 would, as he says, damage this state and its citizens. But it seems unlikely that in the current superheated political atmosphere people will calmly accept the current high level of immigration, legal and illegal.

Nevertheless, Ungar boldly writes that “In an era of crass materialism and widespread, growing cynicism, immigrants help renew, enrich and rediscover the values of America.

“They stand for entrepreneurship and originality; they believe in, and live daily, many of the precepts that have become meaningless slogans to others--for example, that hard work will bring its rewards.�