A somewhat subdued Henry Kissinger was back among his old crowd tonight celebrating the publication of Volume 2 of his memoirs from his time as secretary of state.

He stood with Happy Rockefeller in her Fifth Avenue apartment for almost two hours receiving some 200 friends, former colleagues, politicians, reporters and others who had lived with him in the period he writes about in "Years of Upheaval."

He was 22 pounds lighter than many remembered him, weight he lost after triple bypass heart surgery five weeks ago, and the operation had obviously taken its toll. He kept up his familiar banter through the endless handshaking, but when he found a moment alone, he leaned against a table and the smile faded.

"Henry, I think you should go now," said Happy Rockefeller. He nodded his agreement.

"I think I should," he said.

Nancy Kissinger explained later that he hadn't been overtired but that he was on his way to a prayer service for his father, Louis Kissinger, who died last week.

But if some of the old fire seemed missing from the dynamic Henry Kissinger, most who came to celebrate his work seemed not to notice. And what a crowd that was--Mike Wallace, David Hartman, Margaret Truman Daniel, Evangeline Bruce, Pierre Salinger, Joan Kennedy, Art Buchwald, Robert McNamara, Ted Koppel, William F. Buckley, Joseph Kraft, Bill Blass, Robert Strauss, Abraham Ribicoff, David Rockefeller, and on and on.

Buchwald brought his copy of the 1,200-page book for the author to autograph.

"I want to ask why I wasn't mentioned--again?" Buchwald joked.

When Kissinger handed him back the book, Buchwald's eyes lighted up. He said, "I'm going to be a chapter in the next volume."

Walter Kissinger said he hadn't yet seen his brother's book because, at $24.95 a copy, "I can't afford it," he laughed.

Author Theodore H. White hailed Kissinger as "the best diplomatic writer since Metternich or Talleyrand . . . It's very close to being immaculate, the delicacy with which he handled Nixon."

Kissinger himself said he didn't know what Nixon thinks of the portrayal of him--"I haven't had a chance to talk to him. I understand he's gone out of the country."

Even the Rockefellers didn't try to disguise how impressed they were with Kissinger's drawing power.

"One of the remarkable facts is he's as visible and has as much influence in the world today as he did when he was secretary of state," said David Rockefeller. "It's astonishing, but then he's just very, very good."

Happy Rockefeller said that she and Kissinger had been friends for 20 years and that she was giving the party for him because "he and my husband worked together for the well-being of their country."

"Jim Brady the New York columnist said it was remarkable there were all these people and there hasn't been a fight yet," said Happy Rockefeller, adding that "it has to be Henry's influence."

Joan Kennedy said that she had been surprised when tonight Kissinger asked about her son, Teddy.

"Mr. Kissinger visited Teddy after he lost his leg. Teddy had one of those pop-up toys--a mongoose--which flew up and hit Mr. Kissinger on the head. He said he was never so frightened before in his life."

There were some with favorite Henry the K stories. Barbara Walters remembered the first time she interviewed him.

"I said, 'What's it like to be a swinger?' He said, 'I love it. Now when I'm a bore, people think it's their fault.' "

Winston Lord, with Kissinger from his days as national security adviser, told about the secret July 197l trip Kissinger made to China. "He left all his shirts behind in Pakistan and I told him that he hadn't sat down with Chou En-lai yet, and he's already lost his shirt."

Evangeline Bruce, whose late husband, David K. E. Bruce, headed the first U.S. liaison office in China after Nixon's historic trip, remembered Kissinger's 1974 visit.

"Despite an interpreter, he and Chou En-lai managed to keep up an extraordinary dialogue," she said.

Nancy Reagan's pal Jerry Zipkin was there, standing in line with another of the first lady's favorites, Pat Buckley, who with her husband will accompany the Reagans to Barbados next month. Later, she said she'd read about the Tuesday night demonstration against President Reagan during his New York visit. "I wonder if you asked three-quarters of those people, whether they knew what they were protesting about."

Another guest, who asked not to be identified, said he thought the demonstration showed Reagan is in "a lot more trouble than he thinks." But for the most part, people skirted weightier political talks to concentrate on each other and the evening's superstar.

Arthur Thornhill Jr., president of Little, Brown and Co., which will publish a third volume of the Kissinger memoirs, predicted the trilogy will be a classic.

"I'm not surprised because I had confidence in Henry Kissinger. But there are only a very few books that survive, and I believe Henry's will be among them. I'm just ecstatic about it."

The praise for Kissinger was echoed throughout the exquisite wood-paneled Rockefeller apartment overlooking Central Park, where a number of the paintings are reproductions. Happy Rockefeller and Kissinger stood against a backdrop of a Matisse mural, which looked for all the world like the real thing. But wasn't.

According to Happy Rockefeller, her husband knew his estate would be heavily taxed, so he decided to leave many of his original paintings to the Museum of Modern Art.

"He said, 'Happy, I can't leave you with all these bare walls,' " she said. "So a lot of these things are reproductions of those original paintings."

Nancy Kissinger said that her husband has another 15 pounds yet to lose and that he is uncomplaining about his diet of chicken and veal with lots of salad. Of her own headlines over a suit filed against her by a woman charging simple assault, she was cautiously taciturn. "I usually don't do things like that," she said.

Kissinger's editor said the party had been planned long before he knew he would have to undergo heart surgery. His doctors gave him the go-ahead when it became apparent he was making a good recovery. "You know Kissinger's like an opera singer," said Gene Young. "His schedule's made up a year in advance."