The word legendary began to attach to Lansdale in the Philippines, where as a C.I.A. operative in the early 50's he met Ramon Magsaysay, a Philippine legislator from the boondocks. He struck Lansdale and Lansdale's superiors in Washington as just the kind of man to wrest the newly independent islands from their corrupt politicians and lead them to American-style democracy. The Lansdale-Magsaysay partnership, amply nourished by overt and covert American money and materiel, brought clean elections, virtually crushed the Communist-led Huk insurgents and led Magsaysay to the presidency of his country. Magsaysay proved to be a tough, resourceful leader, but this notable achievement in benevolent meddling was crippled if not ended (good luck, Mrs. Aquino!) when Magsaysay was killed in a 1957 airplane crash.

By that time the C.I.A. had assigned Lansdale to another problem area. In Vietnam he tried to apply what he had learned in the Philippines about fighting political insurgency - first win the hearts and minds of the people and help them fight with you against the insurgents, then you won't have to destroy them and their villages in order to save them. Lansdale put his theories to work with fervor. Collecting a band of dedicated disciples, he fanned out into the countryside to woo peasants with good works and jovial evenings of folk singing. In the dirty-tricks department, he sent sabotage teams to North Vietnam and waged a propaganda campaign to persuade citizens in the North to go to the South before the Geneva Convention sealed the partition of the country. One of his methods of persuasion was an adman's recourse: the use of a slogan, ''The Blessed Virgin Mary is going south,'' broadcast repeatedly to the North's many Catholics.

While he made friends with many Vietnamese, including Diem, he made bushels of enemies among the American military, civilian officialdom and his own intelligence community in Saigon and Washington. Mr. Currey's story is one of constant struggles to overcome bureaucratic inertia and obtuseness. What Lansdale couldn't accomplish with smooth talk and copious memorandums he attempted by going around or reaching above the bureaucracy. By Mr. Currey's account, Lansdale was the best kind of American adviser, a man who recognized that there was a war that had to be won but determined that it be waged for - and mostly by - the Vietnamese themselves. To others familiar with the man, he was a naive and arrogant interloper who did not really understand the people and culture he was dealing with or the realities of the cold war conflict in Southeast Asia. He was, then, both the Lansdale thinly disguised as Alden Pyle in ''The Quiet American'' and the somewhat more sympathetic fellow barely disguised as Col. Edwin Barnum Hillandale in ''The Ugly American.'' That is considerable notoriety for a man who was supposed to be a covert operative at the time.

After his first influential two-year tour in Vietnam, Lansdale puttered about in the Pentagon's darker passageways. According to Mr. Currey, he argued unsuccessfully against the Bay of Pigs invasion and hoped to be appointed President John F. Kennedy's Ambassador to Vietnam, but instead became the director of Operation Mongoose, which contemplated some very nasty and altogether unsuccessful schemes to satisfy the desires of President Kennedy and his brother Robert to depose Fidel Castro. Lansdale's return to Vietnam was strongly resisted by the Government establishment, but in 1965 President Lyndon Johnson sent him back for three more years as a pacification expert for Ambassador Henry Cabot Lodge. For Lansdale they were frustrating, forlorn years: pacification was only a word. America had taken over the war; President Johnson and Gen. William Westmoreland's strategy of attrition was plunging us into the swamp from which President Richard Nixon and Henry Kissinger would later extract us with little honor intact.

''Edward Lansdale'' is plainly a labor of love. It relies much too heavily on Lansdale's recollections and his tendency to repay old grudges while, as Lansdale himself conceded, embellishing the record where he saw fit. It is clumsily organized and marred by some sloppy errors (Ronald Reagan runs against Walter Mondale for President in 1980, for example). But it serves nonetheless to memorialize a true American patriot, one who believed with passion in his country and its ideals and sacrificed much for them. Until the very last, he went out to the flagpole in front of his home near Washington to raise and lower the Stars and Stripes every day. By then, Edward Lansdale had become The Sad American.