A TIME OF CHANGE; By Harrison E. Salisbury; Harper & Row; $19.95.

Although Harrison Salisbury has been a newspaperman for more than 50 years, he has retained the passion for getting to the truth - to the heart of a story - worthy of a cub reporter on his first assignment. If a reporter is not a "disturber of the peace," Salisbury says, "he should go into cost accounting.""A Time of Change" is a wide-ranging memoir from this longtime New York Times reporter and editor, a continuation of the story that began in his 1983 autobiographical book "A Journey for Our Times." But it is much more.

If Salisbury were only to record his reporter's experiences, the stories he has covered, the world leaders he has known, the changes in the world he has lived through, he could tell a head-spinning tale worthy of any reader's time.

Among his reporting triumphs was his ominous (and true) series on the beginnings of the civil rights movement in the South, a series that cost the paper millions in legal fees until Salisbury was vindicated. He covered the 1968 Democratic convention in Chicago. He went to Hanoi during the Vietnam War and reported on the destruction of life and property caused by the American bombing there, incurring the wrath of Lyndon Johnson. He traveled to countries in the Far East no one had entered in years.

Chronologically, this memoir covers the years from the mid-1950s to now. But the book is anything but a chronological diary.

Salisbury is particularly good at drawing pictures of the people and places he has come across through the years. His description of the city room of the paper in the mid-'50s is a piece of beautiful prose, full of nostalgia and love.

Salisbury reveals some of his reactions to U.S. presidents he knew. Richard Nixon and John F. Kennedy were alike in hating the press, he writes, but J.F.K. was better at hiding it. Lyndon Johnson had a mean streak and wouldn't listen to any disagreements with his policies. When he first met Robert Kennedy, Salisbury thought him an arrogant brat; he later believed Kennedy had changed and grown enough to be a great president. He wept at the news of his assassination.

His adventures make incredible reading and have the virtue of reminding us of so many of the significant happenings of the recent past that tend to be forgotten.

The invaluable ingredient that Salisbury adds to all this action reporting in "A Time of Change" is the wisdom gained through decades of observing and pondering over how human beings, high and low, write the history of their times.

Salisbury basically has an optimistic nature, he says, and a belief in the ultimate good sense of mankind, especially Americans. He quotes the Scripps Howard motto: "Give light and the people will find their own way," but he is worried that "the world of electronic journalism, once sparkling with men like Edward R. Murrow and Walter Cronkite (has) slipped into a gray wasteland with bottom-line barons taking it over."

He is concerned the press does not investigate mysterious events that are signs of underlying threats.

"Above all, I seek to spell out the virtue and total necessity for our society of reporting the unpopular event at the most - especially - at the most difficult, touchy moment."