THIS is the third volume of Edmund Wilson's note-books and diaries to be posthumously published, and in important respects the most interesting. In The Twenties, Wilson was a young man enjoying (not to mention graphically recording) the fruits of the decade's sexual liberation, testing his toe in the literary waters, but doing relatively little durable work of his own. In The Thirties, like so many other intellectuals of the day, he turned his thoughts to politics and his energies to political causes, interests that helped lead him to write To the Finland Station, his study of the makings of the Russian Revolution. But it is only now, in The Forties, that he puts these fundamentally peripheral concerns into proper perspective and concentrates almost singlemindedly on the main business of his life, literature.

The central theme of The Forties is the domestication of Edmund Wilson: the dissolution of his unhappy, competitive marriage to Mary McCarthy, his purchase of the house on Cape Cod that gave him privacy and contentment, the marriage to Elena Mumm Thornton, who, as Leon Edel puts it, "was European and therefore clearly conscious of her husband's needs." Edel quotes a letter from the poet Louise Bogan, who visited the Wilsons at the Cape and reported: "For the first time, poor Edmund has attention, space and effectively arranged paraphernalia of all kinds--Mary never really helped in the more practical ways; and Edmund has had a very scrappy kind of life down the years. Now all moves smoothly; tea on a tray for his 'elevenses,' absolute silence in his working hours and good meals at appropriate intervals." Edel, whose splendid introduction leaves little else for the reviewer to say, writes:

"Distinctly absent from the 1940 journals are the events of the war, except for some brief thoughts about the bombings of cities set down in 1944 and the 1945 journey to Europe. The journal records, rather, his walks beside the New England ponds, his love affair with Elena, his period in Reno waiting for his divorce, and his usual notes on talking and drinking with friends and acquaintances. And yet in certain ways the fragmented forties have a greater solidity than his two earlier volumes of the preceding decades. There is a maturity and self-confidence, the sense of authority of a man who has found his course and knows where he is going. As always, there is much routine and even turgid material; but with this there are many felicities of observation and feeling."

Indeed there are. Although The Forties is the least complete of Wilson's journals (he had not gotten around to editing it before his death in 1972), it nonetheless contains a remarkable amount of polished and pointed prose. As is generally conceded, he was the great American critic of his time, a social and cultural observer of sharp insight, and a lapidary stylist; an excellent primer that reveals Wilson at his best is now available in the Viking paperback edition of The Portable Edmund Wilson ($6.95), edited by Lewis M. Dabney. But these notebooks and diaries demonstrated that the distance between raw Wilson and finished Wilson could be very short. Here, by way of proof, is a lengthy passage from the notebooks written in the New Jersey town where he was born:

"Red Bank, July 18, 1944.--Walking down and looking at the Shrewsbury and going into the woods on the road past our old house to the Rumson, where I used to go as a child. America: It still seems even to us a country strange and wild. It is as if we had just sailed into this estuary and found the quiet little harbor with its pale opaque blue-gray waters, half brackish and half salt, tranquilly rippled with evening and the little white moored launches, with the birds flying over the water and the grassy and wooded banks--as if the little white sailing boats against the gold sun had just found themselves there themselves. What a good place to build a house--among the trees by the tranquil water. And so in the woods with its big old trees and its towering seed- tufted ailanthus, its blackberry bushes and its carpet of vines--in the swamp below we used to find skunk cabbage. There was a little white farmhouse and a neat plowed field where the land had been cleared right beside, the uncouth and yet comfortable tangle of that one spot of earth that had never been cleared among estates richly landscaped-gardened--the wonderful solitude and space and peace--the country which we still found and to which we were still new."

Had Wilson had the time to edit that passage, he might have condensed and smoothed it, but it is difficult to believe that he would have fundamentally altered it; as a description and evocation of the American myth of the new-found land and the romance of the frontier, it is multi-layered, sensitive and telling. Indeed, in these journals we find Wilson coming back over and again to the American past and the national mythology--locating his roots not in the Continent, as up to then had been common among insecurity-ridden American intellectuals, but in "the Americans, the frank, the free, the first, the adventurous, who had lived in the society that Jefferson had said was something new under the sun." It is in this volume more than in either of its two predecessors that we can see the beginnings of the masterly work of Wilson's later years, the studies of the American literary and mythic past on which his reputation will surely rest.

By the end of the decade Wilson was in his mid-fifties and possessed of a gloomy knowledge of mortality. In 1949 he wrote: "In this volume, I am constantly writing about death, illness, and decay of old friends." The previous summer, after a visit to his old lover Edna St. Vincent Millay, he had written: "I reflected in dismay, but not without some satisfaction, at my own relative competence and health, on the tendency of the writers of my generation to burn themselves out or break down: Scott and Zelda, Phelps Putnam (just dead), Paul Rosenfeld, Elinor Wylie, Edna. One didn't really believe till one saw it demonstrated that giving oneself up completely to art, to emotion, to enjoyment, without planning for the future or counting the cost, produced dreadful disabilities and bankruptcies later."

This Edmund Wilson declined to do. The decade of the 1940s was the time in which his basic sturdiness of character asserted itself; in what seems to have been a titanic exertion of self-control, he turned away from the dissipation and frivolity of his youthful years and immersed himself in the monumental labors of his lifetime. Halfway through his sixth decade, he had more than 20 years of writing to do, and his greatest work lay ahead of him.