President Reagan's inclination to believe that the Soviet Union is obsessed with fear of U.S. power because of invasions throughout history stems from a romanticized cultural history of czarist Russia that some administration officials wish he had never been given to read.

The president read "Land of the Firebird" last autumn and invited its author, Suzanne Massie, to brief him. The exposition of her Russian sentiments came at lunch in the White House just before his 31/2-hour session with Foreign Minister Andrei Gromyko last Sept. 28. Massie was one of many experts, including Henry Kissinger, who prepped the president for his Gromyko talk, which ended three years of worsening U.S.- Soviet relations.

The senior aide who steered Reagan to Massie's cultural history is no Soviet scholar and consequently failed to anticipate its effect. "The president is a romantic, and therefore highly emotional," a former aide familiar with both the man and the subject told us, explaining why the book was bound to have a "terrific impact" on him.

That impact seems partially responsible for Reagan's opinion, stated several times recently, that the Soviets "have suspicions they think are legitimate with regard to our intent." It also helps explain his unexpectedly quiet reaction to the slaying of Maj. Arthur D. Nicholson Jr., during a routine snooping mission at Soviet facilities in East Germany.

Ironically, a single sentence from Nicholson's master's thesis (published by the Baltimore Sun last week) may reveal Soviet motivations more accurately than Massie's voluminous recital of explanations for Russian fear. "The Soviet alternative (to mutual deterrence) is a concept of peace founded on (superior) strategic power," he wrote.

Massie's colorful history of czarist Russia stops before the October 1917 Bolshevik revolution. Her only mention of Lenin reveals that his grandfather was born a serf. What clearly moved Reagan are her vivid descriptions of foreign invasions.

"The Russian land was conquered and covered with blood, every Russian town . . . burned and sacked" after the Mongol invasion in the 13th century, she writes. She quotes Napoleon 600 years later watching Moscow put to the torch under Russia's scorched- earth policy: "To burn one's own cities . . . what savage determination! What a people! What a people!"

Contradicting Reagan, skeptics disavow the theory that supposed Russian fear explains historical Russian expansionism, which communism has now brought to its zenith. "That theory makes Russian history appear just the way the Russians want it perceived," Zbigniew Brzezinski, President Carter's national security aide and occasional adviser to Reagan and Secretary of State George Shultz, told us.

The notion is also contradicted by Prof. Richard Pipes of Harvard, Reagan's former adviser on U.S.-Soviet relations. He has written that out of 38 Russian wars during the 18th and 19th centuries, 36 were offensive, only two defensive. Czarist Russia's seizure and occupation of the largest land mass by any nation by the end of the 17th century seems more relevant to current U.S.-Soviet relations than dubious historical theories of how past foreign invasions affect current policy.

In the opinion of the murdered Nich Soviet conduct, if believed, might soften U.S. policy. Nicholson, who had connections at high Pentagon levels unusual for a major, described the U.S.-Soviet relationship in uncomplicated terms: The United States should acknowledge the lack of consensus on which to build true cooperation "at least for the foreseeable future." He asserted that "unilateral restraint and accommodations" would be "interpreted by the Soviet Union not as an invitation to cooperation but as an opportunity which must be exploited."

Having read Massie, the president owes it to himself also to read the murdered Nicholson and salt his romanticism with realism as he prepares himself for the summit.