AND WHAT is John Putnam Thatcher, the banker-sleuth of Emma Lathen's delightful mystery series, doing on the snowy slopes of Lake Placid?

Well, Thatcher knows full well that "going for the gold" can mean different things to an Olympic athlete and a thief with a money-making scheme. In Going for the Gold (Simon and Schuster, $11.95), Thatcher, the senior vice president of Sloan Guaranty Trust, comes to Lake Placid to check on Sloan's operations as the official bank of the Winter Olympics. Of course, he also has to play nursemaid to Brad Withers, the bank's playboy president, who is serving on the Olympics Committee.

The two are watching a practice run when Yves Bisson, the French contender for the gold medal in the ski jump, suddenly tumbles to earth from graceful mid-air flight. A bullet, not a bad jump, has ended Bisson's life and French hopes. Once again Thatcher finds himself in the midst of a murder investigation.

Then the Sloan branch manager reports $500,000 worth of counterfeit European traveler's checks have turned up in the bank's vaults.Is one of the athletes trying to carry off more than a gold medal?

A blizzard disrupts the best-laid plans of the culprit, and Thatcher and the police race to save the life of another skier hurtling down the slopes of Lake Placid.

Detection is only part of the fun in the John Putnam Thatcher mysteries, which have already seen the banker clearing up financial shenanigans and murder in fast-food restaurants, the auto industry, a professional hockey franchise, and the Oriental rug business.

Lathen (the collaborative nom de plume for Martha Henissart, a lawyer, and Mary Jane Latsis, an economist) is a witty and sharp observer of scene and people. She can be wickedly funny when it comes to describing negotiations between starchy Olympic officials, held hostage in a ski lift, and Swiss radicals (the Swiss, of all people!) protesting the disqualification of a female skier whose urine test was positive for drugs. Another diverting mystery-cumnovel of manners from the Lathen collaborators.

And what is Bernie Rhodenbarr, the bookseller-burglar, doing reading Spinoza at the funeral of his favorite fence?

You will find out in The Burglar Who Studied Spinoza (Random House, $8.95) when Lawrence Block takes readers on another hilarious caper with Bernie, the hip-talking antiquarian book dealer who gets itchy fingers whenever he sees a locked safe.

Bernie and Carolyn, the lesbian dog-groomer who has become his amateur partner, don their rubber gloves with cut-out palms and break into an empty townhouse, only to find some one has trashed the place earlier. But the locked safe yields some jewelry and an old coin. Abel Crowe, a fence who indulges in pastry and philosophy, thinks the coin may be a 1913 Liberty Head V-Nickel worth at least a quarter-million dollars.

Then the lady of the townhouse is found dead -- victim of a third set of burglars? -- and Crowe is murdered in his fortress apartment. The first murder isn't that difficult to guess, but Block comes up with a whopper of a solution for the second. Bernie fingers the killers at a memorial service for Crowe, sprinkling quotes from Spinoza and Hobbes into his funeral oration. Mystery writers with the comic touch are rare, and Block is one of the best.

And what is a poet doing writing a straight mystery?

Richard Hugo, editor of the Yale Series of Younger Poets, has done just that in Death and the Gold Life (St. Martin's, $10.95). It has a likeable hero, solid detection, atmosphere and believable characters.

Al Barnes, a Seattle cop, takes a job in the big-sky country of Montana. He's found a warm woman to love and a good life disrupted only by occasional drunks and over-exuberant teenagers. Then come two brutal murders, a fisherman hacked to death on the shore of a lake and a local plant official found with a split skull.

Barnes follows links to a psychotic killer and soon finds himself in a motel room with a 6-foot 6-inch naked woman intent on killing him. But the second murder doesn't fit the pattern of a maniac on the loose. Barnes goes to Portland to find that the roots lie in a girl's death to a party 19 years earlier with revelations worthy of Ross Macdonald.

Hugo tells a straightforward story. But there is a touch of the poet in such lines as these: "I imagine he remembered a lake long ago and a girl he saw there and that he heard some old music before he had the briefest sense of pain and the black took over forever."

One of those quiet English villages (which certainly have one of the highest homicide rates in mystery fiction) is the setting for murder in Elizabeth Lemarchand's Change for the Worst (Walker, $9.95). Again secrets lurk beneath the tranquil surface as Detective Chief Superintendant Tom Pollard investigates the death of the curator of a stately home managed by Heritage of Britain. The characters are pleasantly quirky, but Lemarchand, usually a deft plot-maker, has to resort to a hard-to-believe coincidence -- the mugging of Pollard's London neighbor in an Italian cathedral -- to reach a solution.

Joe L. Hensley, a former prosecuting attorney recently appointed to a judgeship, writes mysteries featuring a hard-nosed Indiana lawyer named Don Roback. In Outcasts (Doubleday Crime Club, $9.95), Roback goes back to the small town where, as a child, he came to stay with two great-aunts who had taken in his dying mother.

His cousin, a big hulk of a man, has been accused of murdering his mistress in the big resort hotel that dominates the town's economy. As his great-aunts rock on their front porch, Roback finds out nasty things about local politicos, gangster connections at the hotel, and a United States senator who wants to be president. The ending is a shocker, but Hensley has played fair with the reader.

A Crime Story (Delacorte, $9.95) is the first fiction offering from Jay Robert Nash, a Chicago journalist who writes two syndicated columns on crime. He writes about a character that he should know well -- Jack Journey, his narrator-sleuth, is also a true-crime writer and historian.

Journey leaves his typewriter to serve as a press liaison for the governor, whose son has been mutilated and murdered. It is a messy case and a messy plot. But Journey has a certain charm as a mildly cynical, tough guy who jabbers on about famous crimes of the past. And he's nice to dogs. Nash needs to clean up his jumbled story line, but he can write crisp dialogue and he captures the gritty atmosphere of Chicago.

A good beginning bogs down in talky chat and murky plotting in Weep for Her (St. Martin's, $9.95). Antony Maitland, the barrister-detective of the long-running series by Sara Woods, agrees to help his uncle, Sir Nicholas Harding, in the defense of a "trance medium" being sued under the Fraudulent Mediums Act. The plaintiff claims that his wife's suicide was prompted by messages received from a dead son during a seance. Woods starts off well enough with intriguing glimpses into psychic phenomena, controls, spirit guides, and automatic writing. Then it's downhill from there to a contrived solution that requires a last-chapter summation.