More than ever before in his 20 years of writing about the murky world of spies, John le Carre' has himself come in from the cold this spring, joining in the bally-hoo surrounding publication of his best seller about the Middle East, "The Little Drummer Girl."

Suddenly, le Carre' seems to be everywhere, profiled on the "CBS Evening News" and in Newsweek, interviewed at length on the front page of The New York Times Book Review, writing vigorously in his own defense to counter criticism in The Washington Post.

Le Carre' (nom de plume for David Cornwell) has benefited in the past from the aura of mystery he has kept about him. But this time, recognizing that his sympathetic portrayal of Palestinians and their struggle for a homeland might make the book controversial, he decided to explain his feelings publicly rather than let critics interpret for him. He says he also began to feel that on the Palestinian issue he has a responsibility--for moral reasons--to be outspoken.

"I feel for their injustice," le Carre' said. "I feel a sense of outrage. That is not to exclude the Zionist ideal, but the Israelis have had their special relationship. They have had massive indulgences. I think now the time is right to do something for the victims of their great experiment."

Le Carre' lists other reasons for the high media visibility he has recently attained on both sides of the Atlantic and for his uncharacteristic decision to encourage it.

First, the successful television serializations in recent years of two past books--"Tinker, Tailor, Soldier, Spy" and "Smiley's People"-- have made him, unavoidably, more of a celebrity than before. "The ordinary process of exposure," he modestly called it the other day, in a morning of talk at his London home, a comfortably well-worn red brick house of Victorian vintage near the rolling hills of Hampstead Heath.

There are already 450,000 copies of "Drummer Girl" in print in the United States, plus similarly impressive forecasts for other countries. A major film version is in preparation, to be directed by George Roy Hill, who did "The Sting" and "The World According to Garp."

His second reason for going public, le Carre' said, was his own hard-headed business judgment--a concern that after so long associating him with one set of themes, book buyers might find his shift of direction away from the Cold War to Palestinians and Israelis confusing. Gone for now are such le Carre' staples as the Circus (fictional home of British intelligence) the estimable George Smiley and Karla, the Soviet master agent.

"As far as the trade was concerned," he said, "there were two ways of treating this book. One was to say 'Oh well, we've lost the Smiley audience, this is an off book, let's wait until he does Smiley at Easter or Smiley at Christmas.' The other way was to celebrate it as something new and a bridge to other kinds of writing . . . I thought by coming out and being visible, it would be possible to make a bridge between Smiley and whatever lies ahead."

But the most important explanation for his different approach to "Drummer Girl" is the book's complex perspective on the Middle East.

The heroine, a young left-wing actress named Charlie, is recruited by the Israelis to infiltrate a Palestinian group responsible for attacks on Israelis in Europe. She does so, but in the process, the Palestinians cease to be merely stereotypical terrorists and become bearers of a deeply felt and legitimate grievance.

Le Carre''s own change of perspective was, apparently, a gradual one. Speaking in the deliberate manner of a man who chooses words for a living, le Carre' said his judgments were the product of extensive research in the Middle East over a period of years, trips to Palestinian camps and the witnessing of Israeli wrath visited on civilians as well as fighters. Events, particularly Israel's invasion of Lebanon last year, served to give his account and his opinions greater urgency.

"The book," said le Carre', "is about a balance of compassion. I came into the subject using the conventional formula of a pro-Israeli story but then I began to tamper with the equation and make it more two-sided . . .

"The whole brunt of anti-Palestinian propaganda has been to dehumanize them; all the old racist criteria have been revived in a quite sophisticated way to convince us that these are a people who do not deserve the world's sympathy and since, finally, I'm not a very political person, I think I can help to correct the image . . .

"The huge majority of Palestinians are noncombatant victims. The curious thing is that the Palestinian struggle is in their hands and not in the hands of the fighters because, as with the Jews in their dispersal, it is up to the civilians to indicate how much they can take. The responsibility for survival was with them, with the women and the kids, the families. So far, at least, the Palestinians have shown they can take any amount and the persecution tempers their resolve. It's counterproductive to bomb the camps, displace 800,000 of them . . ."

Le Carre' said he had anticipated negative reaction to the book--especially among American Jews, who he thinks are less realistic about the Middle East than the Israelis themselves. But the feedback has surprised him: "We've had tremendously bonny reviews from coast-to-coast in the States," he said. "I've also been spoken of very pleasantly in the two major Israeli newspapers, Ha'aretz and Ma'ariv. Chaim Herzog, who has just been elected Israel's president, said he liked it."

Le Carre' seems to be feeling more strongly about the Palestinians as time goes on. The architect's table in the small upstairs room where he writes is strewn with papers and documents for a nonfiction piece he is writing on the Palestinians for the London Observer. It is based, in part, on a recent trip he took to Tunis, headquarters for the Palestine Liberation Organization since its ouster from Beirut. Handwritten pages of a draft are being punched into a word processor by le Carre''s wife, Jane.

But despite his convictions, le Carre' definitely does not see himself becoming a permanently public figure, promoting each book as an author-activist would, regularly being interviewed in the media or signing petitions.

"I've done terribly little in the past and I expect I'll do terribly little in the future," he said, " This just seemed to me to be the book where I had to come out and talk about it and be ready to face the flak. Maybe even take some punishment." Chuckling, he added: "I'm doing one more interview tomorrow, with the Jerusalem Post. After that I don't think I'll be seen for years."