SUMMER READING ISSUE : Truth That’s Stranger Than Fiction : FICTION : DISPATCH FROM A COLD COUNTRY,<i> By Robert Cullen (Ballantine/Fawcett Books: $21; 400 pp.)</i>

At a climatic moment in Robert Cullen’s “Dispatch From a Cold Country,” Colin Burke, a newly minted Washington editor who is briefly back on his old Russian beat, stumbles onto a major story. Burke knows he’s got a rare scoop; he’s also got a true reporter’s dilemma. Does he go with the facts or go with the truth?

“Facts were what you could support from quotes or direct observations. The truth was merely what you thought you knew.”

Burke chooses to go with the facts.

At a time when the news columns of major dailies are filled with analysis masquerading as reportage, Burke’s decision is admirably old-fashioned. But what is virtuous in a journalist is not necessarily laudatory in a novelist.

From the time of Joseph Conrad, good spy fiction has always been anchored in fact. Novelists as different as Eric Ambler, John Le Carre and Ross Thomas built their careers on verisimilitude. But these masters never forgot that fiction’s first purpose is to tell the truth that facts cannot. Cullen is not yet in their company.

When he is presenting us with facts, Cullen’s a riveting writer. His opening description of the “tired, cold” Hotel Northern Worker is enough to make any would-be St. Petersburg tourist double-check her travel agent’s recommendations.

A former Moscow correspondent for Newsweek, Cullen is as convincing describing the inner workings of a Russian murder investigation as he is venturing into a financially strapped Italian monastery. He also knows how to tell a story--”Dispatch From a Cold Country” is an intricately plotted thriller that involves the treasures hidden in the Hermitage’s vast collection, the inner workings of the Russian Mafia and a Russian election that sounds suspiciously like the current campaign.

Cullen manages to tease us with bits of information while slowly and quietly building suspense. Rest assured when an obnoxious American businessman stumbles into Burke’s Washington office that he will reappear at a crucial moment in St. Petersburg--but even the savviest reader of thrillers will be hard pressed to anticipate the businessman’s later role. Best of all, when that surprise comes, it seems both just and utterly diabolical.

Cullen even manages that great rarity--a macguffin that is believable, truly staggering in its value and (for once) not a Maltese Falcon-like chimera.

It’s when he gets to the truth that Cullen runs into trouble.

He’s created a rogue’s gallery of minor characters, the best--by far--being the snobbish, greedy London art dealer Charles Hamilton Merrill, whose punctilious ego unravels a truly well made scheme. Merrill is a wonderful example of a character’s essential nature determining the outcome of events.

Unfortunately, Cullen achieves nothing approaching this level when it comes to his hero and heroine. Both Burke and the sympathetic CIA agent Desdemona McCoy are little more than a collection of attributes.

Burke is that familiar shambles: the divorced newspaperman fighting his editor and alcoholism. McCoy is beautiful, overeducated and suspicious of her Langley bosses. They use each other, fall in love and lust with each other, but--unlike with the minor characters--nothing in their natures is surprising, revealing, or essential to the story at hand.

Cullen is so good at detail and plotting that we nearly overlook this failing. Alas, “Dispatch From a Cold Country” is so sloppily edited that we are pulled outside the story again and again. Bits of information are frequently repeated: Andrew Mellon’s buying of Hermitage cast-offs is mentioned twice; a particular Renaissance painting technique appears three times in nearly identical language.

The first time a source asks Burke for money, he reflects that American papers refuse to pay for information, not out of ethical concern, but merely out of respect for profit. That’s a nice, refreshing bit of cynicism. When the same statement is repeated nearly verbatim 50 pages later, however, it’s not nearly as impressive.

Then Cullen gets his plot rolling once more--the book’s final third is the stuff that keeps readers up well past bedtime. Piece after piece of the puzzle falls deftly into place, as the military, the Russian Mafia, and the staff of the Hermitage converge in a gruesome fury. Only afterward do you realize that this is a novel in which we worry more about the fate of the world than that of the main characters.