THE EDITORS of these letters tell us that nearly 2,000 of them, in whole or in part, have previously appeared in print. Why then another, more elaborte edition, of which these three volumes are only the first half? The reasons are plentiful and persuasive. Among them are serious deficiencies and omissions of previous editions and the present availability of considerably more than twice the number of letters heretofore published.

Additional reasons are the dozen or so biographical volumes and special studies of Henry Adams published in the last 30 years that have enhanced his stature and established him as a major American writer. As the editors say, Henry Adams has become "an indispensable figure in American thought" during the 60 years, 1858-1918, covered by his correspondence. No mind more richly furnished and widely ranging appeared among his American contemporaries, and certainly none of comparable distinction has ever been dedicated to the study of history in this country.

Apart from their obvious value for historians, other treasures oof The Letters depend on what the reader is seeking. If it is autobiography, there is far more of that here than in The Education of Henry Adams, which was posthumously and erroneously given the subtitle, An Autobiography. If it is the period and its drama of events, here was a reporter with a box seat and inside information. If it should be the life of the mind, Adams read everything of consequence and usually knew the authors. His picture of transatlantic society is filled out by foreign correspondence and residence abroad about half the time. Seekers for the exotic will find nothing richer in travel literature than his diary-letters from the long stay in the South Pacific islands. And the universal taste for love letters is served by the long withheld or doctored letters to Elizabeth Cameron, the beautiful young wife of the senator from Pennsylvania.

The autobiographical component of the letters is supplemented by the only surviving parts of the Adams' diary, a year and a half of it, 1888-1889, printed in full for the fist time. In the diary he breaks through the restraint and understatement imposed on references to himself in letters. The letters begin in 1858 with the youth of 20 on the grand tour in Europe trying his wings as scholar and journalist and relishing his coup as the first American to interview the revolutionist Garibaldi. Then comes the secession winter in Washington, when he confesses to his brother Charles Francis his hopes that "a century or two hence ... my letters might still be read and quoted." In 1861 he is off to London as secretary to his father, minister to Britain during the war and three years thereafter. Back to Washington in 1868 as a muckraking journalist during Grant's first administration, and thence to Harvard in 1870 as an assistant professor of history, "not so much to teach as to learn," but "utterly and grossly ignorant." While learning and teaching he took time out to marry Marian Hooper and take her up the Nile on a honeymoon. In his spare time he also edited the North American Review, leading magazine of his day, and explored the Wild West.

Seven years of Harvard were enough, and in 1877 he and his wife rented a house on Lafayette Square opposite the White House and Adams set up in Washington as an independent scholar and man of letters. His big project was what grew to be a nine-volume history of the Jefferson and Madison administrations, in which he proposed "to tell the whole truth." A year and a half in European archives with his wife expanded the project with exciting new sources. While the major work went forward, minor books -- novels, biographies, monographs -- spun from his pen in an explosion of creativity. "John Randolph is finished. Rah, rah, rah! Now for Aaron Burr." Half the fun of his novels of political and social criticism, Democracy (1880) and Esther (1883), was the tight conspiracy of anonymity and the game he and Marian played of accusing intimate friends of writing them.

All this took place in a magic circle of intimates Adams described to an English friend as "the jewels oof my generation; all the friends I have that count in lilfe here." At the center were "The Five of Hearts" -- the Adames, the John Hays, and Clarence King, and in and out of the house were the foremost or future stars of American architecture, painting, and sculpture, as well as prominent historiams, writers, scholars, and scientists. There was an almost giddy perfection to it all: "I write and ride and dine and chatter all I can with all who care to waste their eternal souls in that frivolity," Adams wrote with characteristc self-deprecation. Actually he savored every moment of it, and at his side was "the only woman in the world who fits my cravings and never sounds hollow anywhere," as he wrote her. These enchanted years ended catastrophically on December 6, 1885, with Marian's suicide. She was one of three siblings who met the same end.

Numb with grief, Adams carried on with outward stoicism, admitting that "for twelve years I had everything I most wanted on earth." He moved into the handsome new house he had just completed for Marian by the side of one John Hay built at the same time, where the Hay-Adams hotel now stands. He plunged for relief into the intense work of completing his big history and sought distraction in travel to Japan and Cuba. While he was at home his breakfast table, usually set for eight, was often ornamented by admiring women and friends. Some of the old gaiety seemed to be restored. But his diary reveals underlying all this much world-weariness, alienation, depression, and the grimmer stages of grief.

Two developments coincided to cast him loose, break old chains, and begin a new life. One was the completion of his nine-volumne history. The other was a crisis in his relations with Elizabeth Cameron. The young woman became an intimate of his circle and a friend of his wife before her death. Adams virtually adopted her infant daughter Martha and focused his love of children on her. But then his feelings toward Elizabeth intensified to the point of an anguished passion that seemed destined for nothing but intolerable frustration. The need for escape became urgent, and in 1890 he sailed from San Francisco, more in flight than in quest, for the South Seas. With him as his traveling companion and guest was John La Farge, the painter and writer, who had earlier accompanied him to Japan.

Their itinerary and way of life were not those of tourists. Their stops and the duration of their stays were dictated by impulse and local interests, and prolonged by attachments to the native friends they made. La Farge wanted to paint, of course, and instructed and encouraged Adams in the art. But the teeming mind of Henry Adams came alive with responses to the anthropological, geological, scientific, and human wonders daily encountered. His visits, some prolonged for several months, included Hawaii, Samoa, Tahiti, and the Fiji Islands. A four-month visit to Tahiti taught him the ravages of imperialism but resulted in his adoption into the deposed royal family and inspired him to write a history (privately printed later) of their lost world.

MEanwhile he kept in touch with his own lost world largely through correspondence with Elizabeth Cameron. He had stocked up with a supply of folio-sized sheets that he filled with what he called "a sort of diary," long dated entries on his adventures that he sent her as letters. It is misleading to call them love letters, since the word and subject are rarely mentioned -- "you must imagine what I can't write." But it is difficult to imagine letters, diaries, travels, storeis written with such richness of feeling, sympathy, color, and emotion save by a man in love: "what a responsibility a woman assumes in being a female," he remarked in an aside. At what was then breakneck speed he continued his circumnavigation of the globe in order to meet her in Paris, only to be greeted by an "apocalyptic never."

But that was not quite the ned of the story. Those who continue with it, to judge from the part published, will be in the hands of capable and scrupulous editors. Their work has been conscientiously and skillfully done, and it is a pleasure to recommend these volumes.