You can't tell a book by its cover, but covers do sell magazines.

Some covers attract with information, as in Cosmopolitan's famous blurbs, this from its best-selling January 1979 issue: "The New Chastity. Why More and More (Desirable) Women Are Dropping Out of the Sexual Rat Race." Others are more visceral: The National Lampoon's famous gun-at-the-dog's-head cover, headlined: "If You Don't Buy This Magazine We'll Shoot This Dog!"

Newstand browsers are barraged by covers. Art directors rise and fall with the success of their covers. And editors are ultimately held responsible for them. Last year, when Ed Kosner was dismissed as editor of Newsweek, one of the most frequently cited reasons was his love of soft feature covers: While Time was touting Pope John Paul II in Poland, Kosner went with "Alien" star Sigourney Weaver and a cover on horror films.

Despite the vagaries of the magazine business -- problems with distribution; subscription versus newsstand sales -- magazine cover sales are one barometer of popular taste.

Time Inc.'s interest in lauching a new science magazine called Discover was promoted by the generally favorable response of readers to Time magazine's science covers.

"Our sience covers were way up" again this year, said one Time source, although the magazine's best-selling cover was about drug smuggling and its second-best was one called "How Gay Is Gay?" Time's worst: Columnist Russell Baker. Interestingly, Time's first issue of 1980, which named Ayatollah Ruhollah Khomeini Man of the Year generated 1,806 letters to the editor, the most in the magazine's history; 297 readers canceled their subscriptions.

At People which has virtually no subscribers (355,672 versus 2,038,988 newsstand sales), the best seller -- apart from its fifth-anniversary issue -- was a "Mork and Mindy" cover way back in February. By fall, into the show's second season, which fans claim to be much lower in quality, Robin Williams alone managed to be People's worst-selling cover; similarly, Pam Dawber graced Family Circle's worst-selling Sept. 18 issue.

The new life, which in less than a year garnered 1,271,517 readers, did best with its year-end salute to the '70s, followed closely by a January cover on dogs. Dolly Parton was Life's worst seller, though not much worse than the pope. Sports Illustrated's best was its annual bathing suit issue, whose 1980 issue is on newsstands this week. SI's worst was a golf cover, which always tends to do poorly. Last year: Tom Watson.

At Newsweek, which sells 2.9 million copies weekly versus Time's 4.3 million, science covers also did well. Apart from its '70s wrap-up, the best seller was a cover titled "Mysteries of the Universe," followed by an in-depth look at Three Mile Island. Newsweek's worst seller was a shot of Jimmy Carter titled: "Giving Peace a Chance."

Last year certainly did sum up the Me Decade. Readers Digest, whose circulation lags a mere 500,000 behind No. 1-ranked TV Guide (average sales 19,547,763 copies a week, with its fall preview issue a best seller every year), found its most popular cover offered "How to Flatten Your Stomach: Eight Ways to Size 8." (The Digest's worst was "Betty Ford's Triumphs Over Drugs and Drinking.")

At the National Enquirer, king of the pulps with 5 million in circulation each week, the worst seller was concerned with "The Other, Discover Your Loved One's Secret Personality." At Redbook, the "Wise Woman's Diet" ranked first, while "How Loving Partners Learn to Satisfy Each Other" was the decided loser. A Washingtonian cover on the sex life of teen-agers sold best; its worst cover was on old friends. Ms's "Fitness Without Jogging" was its best of the year. The National Lampoon found depression to be a real snore on the newsstands, while its heterosexuality issue did best.

Suzanne Somers put the poorest performance for Ladies Home Journal one year ago on its February cover. This February, wearing less clothing, she has sold an extra 800,000 copies of Playboy.

"Obviously she's a Playboy person and not a Journal Person" says LHJ editor Leonore Hershey.

At Playboy, which increased its circulation 14.8 percent last year (to 5,538,559), Raquel Welch was a handsdown best seller, followed closely by the girls of the Ivy League. Playboy's worst was a James Bond cover in July.

One of the most staggering leaps in the magazine world last year was made by Bon Appetit, which raised its circulation 24.8 percent (to 1,115,563). BA's best seller was a November photo of a Thanksgiving turkey, the magazine's first perfect-bound issue, marketed on newsstands with its selling price increased 50 cents to $1.75. The worst-selling cover was a bowl of strawberry sherbet in july.

Other cover statistics:

Us (circulation 848,343 up 18.2 percent). Best seller: Cher followed by Elvis; worst: a cover on the Oscars, followed by the Bee Gees.

Business Week. Excluding special issues, a Jan. 15 cover on Mexico's oil boom sold best; a Teamsters cover had the poorest newsstand sales.

High Times' best: December's "Highest Holiday Ever," including a marijuana cookbook; worst: July's "Greatest Scams of All Times."

Mad's best; Superman; Worst: Alfred E. painting a playing card upside down. Mad's circulation is 1.8 million. Last year Parker Bros. sold a staggering 1 million copies of a Mad board game. And the current New Republic borrows one of Mad's famous "Spy-versus-Spy" cartoons for its cover.

Forum's best: legs are back and so are stockings; worst: discomania.

Omni's best, excluding its anniversary issue, was August's encounters with Robert Heinlein and Carl Sagan; worst, an exclusive interview with Arthur C. Clark.

The New Yorker's best: Feb. 19 issue with the annual Eustace Tilley cover, containing John McPhee's gastronomically titillating profile on "Otto and Anne," the reclusive restuarateurs who McPhee refused to name in the article but claimed had cooked the 20 or 30 best meals of his life. Worst: a C.E.M. cover of a red snow shovel against a pale-white house, unfortunately released in the middle of last year's overwhelming snowstorm.

Rolling Stone: Best, Ricky Lee Jones; worst, Richard Pryor.

New York: best, "Greatest Photos of New York," followed by "Studio 54: The Party's Over"; worst, a cover on the Cuban nationalist movement in New Jersey.

New West: best, "Goodbye to the Seventies" (humorously run in January of last year rather than in December); worst, "Secrets of the Track," on horse gambling.

Esquire: best, Gail Sheeby's "The Truth About Today's Young Men," with a simple all-type cover; worst, "Hollywood versus Harrisburg." Commissar's Conundrum

With Soviet troops in Afghanistan, Janos Radvanyi, a former Hungarian ambassador, offers a different side of Russia, this one a delightful reminiscence of boar hunting with the late Nikita Khruschev.

In the February Atlantic, the author recalls a tale told by Khrushchev as an example of stalinist diplomacy:

"It all happened in October, 1943, when the British Foreign Secretary, Anthony Eden, and the United States Secretary of State, Cordell Hull, traveled to Moscow to hold talks with Molotov," Khrushchev is recalled as saying speaking of Soviet foreign commissar Wyacheslav Molotov.

"The three drove out to Molotov's dacha. Great logs were burning in the fireplace and a few rounds of vodka had created a rather warm atmosphere . . . Molotov asked Eden and Hull whether they knew how to force a siamese cat to lick mustard . . . Eden placed a spoonful of mustard in the middle of a nice piece of prime rib steak . . . The cat turned away . . . Hall order fish. He put the mustard in the right branchia of the fish with the hope that the cat would start eating it . . . The frisky pussy simply refused to touch the royal meal.

"Last in line came Molotov, wearing his goldframed spectacles -- which always made him look like a high school teacher rather than the deputy of Stalin. He acted resolutely and with great speed grabbed the poor kitty, lifted its tail, and smacked a handful of mustard on the backside of the animal. The commissar then threw the cat down on the floor. And as you can imagine, the poor animal, while screaming and running in circles, started to lick the mustard off." Philosophical Linebacker

Great quotes department. This one from Sports Illustrated:

Dewey Selmon, Tampa Bay Buccaneer linebacker, who is working on a PhD in philosophy at Oklahoma: "Philosophy is just a hobby. You can't open up a philosophy factory."

Grist for the Gifted

Two new ones:

The Gifted Children's newsletter offers monthly both philosophical and practical advice to parent of special children. The first issue includes suggestions on how to approach schools, an essay on parents' rights, a list of recommended games and an article on home computers, as well as a four-page workbook insert designed for gifted children themselves. ($24 annually from Box 2581, Boulder, Colo. 80322.)

Humanities, a bimonthly review of the discipline, published by the National Endowment of the same name, provides an interesting glimpse at grants being handed out as well as tips on how to cash in on this lucrative federal dole ($7 annually from the Superintendent of Documents, U.S. Government Printing Office, Washington, D.C. 20402). With Love, From Loveland

Want the perfect place to have your valentines postmarked? The February Rocky Mountain Magazine suggests mailing your prestamped and addressed valentines in another envelope to Postmaster, Loveland, Colo. 80537, where they'll be canceled with a special sweetheart postmark. Cops and Comedy Good reads:

E. S. Ely's examination of the conflicts generated when police organizations mount fund-raising drives, in the January Police Magazine ($11.97 for six issues from 801 Second Ave., Suite 1404, New York, N.Y. 10017).

New West's hysterical parody of California's Sunset Magazine (Slanted floors make vacuuming a snap") in its Feb. 11 issue.

Fortune's 50th-anniversary issue, a retrospective compendium of the magazine's published work, led by Archibald MacLeish's profile of Ivar Kreuger, who committed suicide when his financial schemes failed, and several portfolios of photographs including the work of Margaret Bourke-White and Walker Evans. Tumult in the Test Tube

The five greatest scientific advances made in the past decade according to the Fellows of Great Britain's Royal Society reported in the February Omni:

Discovery of enzymes that cut DNA into pieces, yielding the possibility of life in a test tube.

Increased understanding of the relationship between electronagnetism and weak nuclear force, a step toward understanding Einstein.

New ways to read the coded messages in DNA, especially the discovery of overlapping genes.

Confirmation that variations in the earth's orbit determine the pattern of Ice Ages.

Detection of background radiation from the big bang that apparently created the Universe. All-Time Champ

The top-selling black recording star of all time is the late Nat King Cole, according to the February Ebony. King Cole has sold 75 million records, followed closely by Fats Domino with an estimated 65 million records solid. The 400

Two good compilations:

The National Journal's assessment of American politicial priorities is $7.95 from 1730 M. St. NW, Washington, D.C. 20036.

While there are more than 12,000 magazines published in the United States, the top 400 of them generate $7.3 billion in sales -- or 94 percent of the magazine industry's annual total. Folio, the magazine for magazine management, has analyzed the top 400 in a special report, $10 from P.O. Box 697, 125 Elm. St., New Canaan, Conn. 06840. Works in Progress

In the works;

Museum, a 96-page, four-color monthly dedicated to all the world's museums;

Dial, a cooperative venture from four PBS stations, including Washington's WETA, with national features and local listings.