Aided by a blizzard of publicity, H. R. Haldeman's "The Ends of Power" made a dramatic leap onto some best-seller lists last week, but there is mixed opinion in the book business about how long it will stay there.

Times Books, the publisher, says the latest Watergate-inspired epic has leveled off into a solid entrenchment among bestsellers. But Newsweek, which paid $125,000 for a two-part, 30,000-word excerpt, says its sales have been disappointing. One Manhattan book dealer claims "it died."

Retail book sellers in New York, Washington and Los angeles noted unusually high sales immediately following the book's highly publicized early release Feb. 17. (These sales can be expected to effect national best-seller lists for another week or two). But most of the dealers contacted expressed varying degrees of disappointment over how it has sold this week.

"The first few days it was a big thing -- I was ringing up 10 or 20 books at a time," said a spokesman for New York's Scribner Book Store. "Now it's negligible.

Considering the circumstances, said Times Books marketing director Leonard Schwartz, the apparent drop-off in the book's sales is "not unusual."

"We're dealing with a phenomenon that never occurred before," he said. "The initial sales were a response to the incredible bombshell of publicity surrounding the book's release."

Schwartz quoted sales figures of a major bookstore chain, B. Dalton Booksellers, which logged "The Ends of Power" as a "solid" No. 1 seller last week.

"Dalton named 'Ends of Power' No. 1 after selling 2,400 copies last week," Schwartz said. "No. 1 seller wek," Schwartz said. "The No. 1 seller the week before was a book on running -- but it was No. 1 at 1,200 copies sold."

Schwartz said the publishers have just finished a third printing, and that 425,000 copies now are in print.

Those book sellers contacted, however, expressed few expectations of prolonged best-seller status.

"People tell me it's just not a very good book," said Jim Tenney of Georgetown's Book annex. "I would've sent back the original order if I didn't have to keep it for three months. It seems to me there were a number of people who just had to have it right away, and they were people like (columnist) Joe Kraft, people with higher-than-average interests in the whole Watergate enigma. . . ."

"We did beautifully with it on Friday (Feb. 17)," said a spokesman at Doubleday Bookstore in Manhattan. "People were buying two or three copies a piece. But they're not buying now. It's not another 'All the President's Men.'"

"It's not another 'Gone With the Wind,' " said a spokesman for B. Dalton's outlet in Hollywood, "but it's been doing okay. . . It hasn't been selling in the whirlwind fashion we'd all expected."

Several book dealers volunteered the explanation that the "conscience factor" accounted -- as they said it did with several previous books by Watergate conspirators -- for the decline in "Ends of Power" purchases.

"A lot of people I saw in the store went right past the book, saying things like, 'I'm not going to buy that guy's book' ro I'm not going to give him my money,'" said Bart Arenson of Discount Books in Chevy Chase.

"Those people," said a spokesman for Hunter's Books in Beverly Hill, Calif., "are in no way unique."

At the Beverly Hills store, which the spokesman said counts Haldeman and family as occasional customers, "The Ends of Power" is "selling well, but it's far from a blockbuster."