<i> Samurai and Silk A Japanese and American Heritage by Haru Matsukata Reischauer (Harvard University: $20; 371 pp., illustrated)</i>

One never knows enough about one’s heroes. One of mine was Prof. Edwin O. Reischauer, the American ambassador to Tokyo from 1961-1966.

He was part of my foreign service dream. As an undergraduate struggling with Japanese at UCLA in the mid-1960s, I had admitted Reischauer to my select pantheon of diplomats who have mattered.

Reischauer had been appointed by President John F. Kennedy to help mend “the broken dialogue” with the Japanese that had followed the humiliating cancellation of President Dwight D. Eisenhower’s planned state visit to Japan in 1960.

Reischauer was one of those “New Frontier” appointments that underwrote the reputation of the Kennedy White House for effective public relations. Reischauer was an immediate success with the Japanese public. He had studied their history, spoke their language, and indeed had even taken a Japanese wife.

So from the beginning, we “knew” about Mrs. Haru Matsukata Reischauer. When Prof. Reischauer’s name was put forward for the Tokyo post, diplomatic circles in Japan made known their “unhappiness” at the prospect of an American ambassador with a Japanese wife. We were then still in the age of official awkwardness over “international marriages.”

At first, therefore, Mrs. Reischauer was not so much a person as a delicate if temporary issue in international relations. We know better now. She is an intelligent and talented woman who can claim a remarkable family lineage. But above all we now know Mrs. Reischauer’s secret: She is a sensitive and skillful biographer and storyteller.

In a book full of charm and insight, Mrs. Reischauer has told something of her own life (one longed to read more) and much about her extraordinary family. “Samurai and Silk” is at once an autobiography, a double biography, and a family saga covering three generations. It is a treat to read.

The core of “Samurai and Silk” is the engaging and instructive story of Mrs. Reischauer’s two grandfathers. The life of Rioichiro Arai (he preferred to spell it that way), her mother’s father, may be summed up as “Japanese farmer makes good in America.”

Silk was Japan’s premier prewar export. Over four decades of a successful business career, Arai was a dominant presence in the all-important New York silk trade. He also introduced the Japanese to what is now their great adult sporting compulsion: golf.

Mrs. Reischauer’s paternal grandfather was Count Masayoshi Matsukata, a feudal official who played a significant role in the Meiji Restoration of 1868, the birth year of modern Japan. He went on to become Japanese prime minister and a powerful elder statesman, but still more important, he was probably Japan’s greatest finance minister in modern times.

These twinned lives--Arai and Matsukata--are well-told episodes of human energy, vision and achievement. Their presence would flatter any family tree.

The last third of “Samurai and Silk” deals in brief with the outstanding family members among the descendants of Arai and Matsukata. The book suffers a bit. The biographies become thumbnail sketches, and the narrative rhythm is rather choppy. But the lives of the later two generations were crowded with fascinating events. One just reads on.

Mrs. Reischauer’s relatives and in-laws alone would form an important chapter in any modern Japanese “Who’s Who.” The Arais and the Matsukatas knew everyone.

As war clouds gathered in the Pacific in the late 1930s, Count Matsukata’s son Otohiko was exchanging personal notes urging peace with one of his old Harvard class- and club-mates: Franklin Delano Roosevelt.

Another Matsukata son was involved in an abortive 1938 plan to arrange a cease-fire between Japan and China.

At the end of the war, one Arai son-in-law actually delivered the disk recording of the Japanese emperor’s surrender speech from the imperial palace to the broadcasting center on a bicycle .

My favorite personality among the younger members of Mrs. Reischauer’s family is Kojiro Matsukata. He was a Japanese cosmopolitan who had studied at Rutgers and the Sorbonne. Kojiro also had a minor passion for fine clothes and quality cigars. He was a member of Japan’s Diet or Parliament, an important early president of Kawasaki Shipyards as well as editor of several influential newspapers.

In his copious spare time, Kojiro collected art. Mrs. Reischauer narrates: “When Kojiro was introduced to Monet, he told the great man that young artists in Japan were studying his paintings through photographs and were most anxious to see the originals. It pleased Monet that Japanese artists were eager to see his paintings because he felt that Japan was the source of his art. Monet rarely allowed the members of his own family or even close friends like Georges Clemenceau to enter his atelier, but he invited Kojiro in and showed him all his paintings, telling him to choose any he liked. Kojiro purchased 16 . . . .”

Much of the book is like this. One tightly drawn vignette follows another. As a biographer, Mrs. Reischauer does not dawdle.

A note of caution. Reading “Samurai and Silk” is a bit like making your way through a Russian novel: The difficult foreign names come fast and thick. But a little patience at the beginning and the occasional reference to the family charts included in the book will ease the reader’s way.

This “parallel lives” is Mrs. Reischauer’s small monument to the values of family, ambition and that supreme Japanese virtue: hard work. “Samurai and Silk” may be the Japan book of the year, and one does not have to be an old Japan hand to savor its pleasures.