UPPER-CRUST Iranians in exile, forever puzzled by the revolution that cast them adrift, point bitterly to the late Mohammad Reza Shah, his arrogance, suspiciousness, and the terrible uncertainty that hamstrung him as radicalism swept Iran.I remember a retired Iranian general, a big, impressive man with a Persian cat beside him, living comfortably in London. He spoke sadly of the Shah's fascination with international military magazines, which he used as shopping catalogs when the oil revenues shot upward after 1973: "We need more helicopters. And tanks, we must buy these British tanks," said the Shah. The general demurred. "Tanks, sire, require mechanics, transporters, spare parts, fuel trucks; it's not simple." The Shah exploded: "Who are you to tell me what to do! I know more about it than you do!" And so on. The general, a staunch monarchist, nevetheless soon chose to retire. The story illustrates the central theme in Marvin Zonis's useful but rather limited psychobiography of the Shah: that deep-seated personality flaws undermined his rule, helping to trigger a revolution that swept away everything he represented. Zonis rightly presents the Shah as a desperately lonely and unhappy man, contemptuous and fearful of everyone, forever struggling with his father's expectation that he be tough, vigorous, aggressive. Meanwhile, the tiny circle of intimates - on whom the Shah depended - started collapsing in the 1970s. All this is true. But Zonis has backed himself into an intellectual corner by placing personality before politics. Many people like to believe that strong personalities can resolve all problems through sheer willpower. Zonis is riding that wave by choosing to entirely ignore the many factors - social, economic, religious, political, psychological - underlying the Iranian Revolution. And he is elevating the significance of powerful leaders - while diminishing that of the revolutionaries - by tacitly suggesting that the Shah could have transformed history if only he had behaved decisively. Why didn't he? Zonis, predictably, finds answers in the Shah's childhood, and readers are carried back to Mohammad Reza at age three, when the household was broken by his parents' angry separation; at age six, when his powerful father took over the child's life; at age 11, when he was suddenly dispatched to a Swiss boarding school for the next five years; and so on. Trauma, loneliness, emotional deprivation: Zonis presents these as the factors that blocked the Shah's growth into rationality and maturity. This is convincing - so far as it goes. But many people experience childhood traumas, only to become reasonable and even admirable adults. Not so with the Shah, who had plenty of enemies. The Soviets, and especially the British, had overthrown and then exiled his father in 1941; the Shah never saw him again. His mother and twin sister harangued him constantly to emulate his father, to be manly and courageous - even as the intelligentsia and the liberals sneered at him as a parvenu whose days were numbered. He was barely saved in 1953 by a CIA-organized coup, and in 1963 by the army's readiness to drown religious riots in blood. The Iranian left and center despised him; the monarchists acc epted him out of necessity, not admiration; and even his American protectors - whom he needed desperately and therefore feared - found him closed, devious, unknowable. The problem - which Zonis, who argues that Iran needed a strong leader, cannot recognize - is that the Pahlavi dynasty was illegitimate and anachronistic from its first days in the 1920s. It was created by force; it ruled by force; it could neither crush nor accommodate its opponents; and it collapsed when its forces evaporated. How sad that American leaders, diplomats, journalists, and intelligence officers were too influenced by their own goals and experiences to be able to understand the great vacuum that was the Shah and his reign.