IN ROOM 513-D of the Health, Education and Welfare building Robert Treuer (GS-15) will soon be sorting his last batch of computer print-outs, checking the drawers of the big desk, taking his peace-pipe and tomahawk down from the wall. By July and August, as most Washingtonians squint against the glare of concrete and marble, Treuer will be with his family on the tree farm - where the Norway pines he planted as seedlings now stand 30 feet tall.

Treuer has written a surprising and affecting book about the place - about his people, his life, and yes, his trees. It's the kind of book that readers get deeply, personally involved with; the kind of book you tell your friends about.

Jim Landis, an editor at Morrow, was especially fond of the manuscript when it came in over the transom, but Morrow, for one reason and another, decided not to publish it. Treuer was going to give the book to a university press. Landis told him to wait; called agent Elaine Markson and recommended Treuer to her. She took him on, mailed out the manuscript, and three weeks later Little, Brown accepted it.

As the book went into producation Treuer called and consulted on everything from copy-editing to illustrations, paper stock, jacket copy, even the typeface. Most writers are not allowed to get involved - or interfere - to such an extent, but Markson says Treuer was "because everyone knew how much it meant to him."

He's a man of startling intensity. Meeting him for the first time one thinks of scenes from the book: the work bee organized to sace the farm and family of a neighbor accidentally killed; the hunt for a pack of half-wild dogs that have slaughtered his child's pet sheep; the forest fire - Treuer driving through smoke and flames, seriously burning his hand and face, then telling the drivers of a vitally needed tanker truck, "What do you mean its risky? I just drove through it to call you. Yeah, sure, its a piece of cake."

There is something of the street-fighter, the agitator, about him. An Austrian Jew, Treuer barely escaped the Nazis as a boy just before World War II. And to some extent the shadow of the holocaust still haunts his vision of the world, separating his book from the mass of "back-to-nature" confessionals that seem by comparison rather frivolous.

In this country Treuer discovered other injustices, found causes - civil rights, the labor movement and later the petty tyrannies of Joe McCarthy. "I never had any trouble finding a fight," he says, smiling. He became the editor of a lobor weekly in Wisconsin, then an organizer for the United Auto Workers at a plumbing factory, "more ardent in the cause of the strikers than the most put-upon worker in the plant."

But there seemed to be an emptiness in all this effort. After a demonstration he helped organize erupted into aimless, rampaging violence, he began to question his motives and goals, the worth of his own life. He felt the need to look closely at himself, "to value the goods," as he says - find some way of leading a constructive existence that was not just a "knee-jerk reaction, an automatically repeated fight against things that were bad simply because they symbolized the enemies of my childhood."

He found the farm: 200 forlorn, infertile acres. He moved there on Memorial Day, 1958.

Treuer writes of all this in a sincere, understated style that is alo, quite often, quietly funny. He chose trees as a crop, he says, because they were all that would grow. previous owners of the land had tried the conventional husbandry of dairy cows and grains, and failed miserably. He considered bee-keeping, but the climate ruled it out. "Another time I raised the prospect of musk oxen," he writes, explaining the pros and cons of the idea. "It was one of the many notions I did now discuss with my neighbors."

He writes crisply and evocatively of harvesting wild rice with the Chippewa Indians, his wife knocking the irregular grains from the stalks with a stick as he poled a canoe through the shallow lakes. He writes of spending one winter day each year sitting silently, high above the ground in the limbs of a jack pine, just to listen to the forest, to watch the animals, to intensify his feel for the place.

Yet Treuer spends most of each year here in Washington, a bureaucrat in a sterile office. He worked in Minnesota teaching and helping to organize the Chippewa near his farm. "I wanted to speed up the process, do something about lost papers, see that people had their questions answered," so when the Office of Economic Opportunity here offered him a position, he took it. Now, after several bureaucratic shuffles, as a "special projects officer" at HEW, he is not sure he made the right decision. "I think we underestimated how we would feel leaving the farm and living off of it."

He hopes to move back for good in a couple of more years; find another job. His wife, a Chippewa, will have her law degree. They and their children will make out all right. The land can't support them, but at least now, after 20 years, it supports itself.

Meanwhile, he takes leave without pay, if necessary he resigns (he has told his superiors that his present job should be abolished, and he returns to the farm in the summers. "Return," he emphasizes, "not retreat."

Treuer, after all, is not interested in escape. What he has been searching for is perspective, and his 20 years in contact with the tree farm seem to have given it to him. Among the stands of Norway pine he has discovered a way of looking at life selectively, finding in it what he needs, and leaving the rest behind.