Why the Shah's world toppled: two views; The Rise and Fall of the Shah, by Amin Saikal. Princeton: Princeton University Press. $14.50.; The Fall of the Shah, by Fereydoun Hoveyda. New York: Wyndham Books. $9.95.

The toppled statue of the Shah outside the Officers' Club in Tehran summed it all up. As Christmas 1978 gave way to New Year's 1979, the forces of a truly people's revolution made it increasingly clear that the Shah's days were numbered. Yet in the midst of the tumult, armed guards kept the Officers' Club physically immune from what was happening outside. And around the corner outside the War Ministry, a heavy tank parked in the main entrance had its gun trained permanently down the street to scare any hostile protesters away.

So it was, until that fateful weekend (Feb. 9-11) of fighting in Tehran, a week after the boisterous return of Ayatollah Khomeini from 14 years of exile, and nearly a month after the Shah's almost smuggled departure from the land he had ruled for nearly four decades. But on the evening of Feb. 12, everything had changed. The tank outside the War Ministry had gone. The statue of Muhammad Reza Shah Pahlavi outside the Officers' Club was on its side -- unsung, abandoned, unattended. In a twinkling of an eye almost, the Shah's trumpeted "great civilization" had crumbled into ashes. And as a final and revealing indignity, the armed forces -- trained for so long to be loyal to the last to their monarch -- had packed up and gone home.

These two books offer an explanation of what went wrong -- or more particularly of what went wrong with the Shah and the institution of monarchy in Iran.

Amin Saikal, an academic of Afghan origin now at the Australian National University in Canberra, offers a historian's balanced account, buttressed by detail and statistics and by native scholarly understanding of the region to which Iran is so crucial. As the title of his book indicates -- "The Rise and Fall of the Shah" -- Mr. Saikal gives equal emphasis to the Shah's initial successes and to his dramatic self-inflicted decline and crash.

Fereydoun Hoveyda, brother of Amir Abbas Hoveyda, a former prime minister of the Shah who was executed by the revolutionary forces in April 1979, gives us a personal perception of what went wrong from the point of view of a man who had a pipeline to the inside, even if he was for the most part in the service of the Shah abroad. At the outset, he asks the indulgence of the reader if his emotion at the "murder of my brother" breaks through his text.

On ly the churlish could fail to respect Mr. Hoveyda for the discipline which he nevertheless maintains. And yet there are times in his book when one is reminded of the tone of some of former President Nixon's associates when they went into print to explain what went wrong to produce the Watergate's scandal.

In the context of the Shah's Iran, the Hoveyda brothers were more honorable than many others serving the monarch (and themselves) at a high level. But as Fereydoun Hoveyda concedes, everybody involved in that system was tainted and tarnished by it.

In the last resort, of course, it was the flawed character of the Shah which precipitated his downfall -- as in the case, incidentally, of Richard Nixon. British journalist Robert Graham summed it all up (in the case of the Shah) in the perceptive title of his book published in Britain early in 1978: "The Illusion of Power." Both the Shah and Mr. Nixon thought they could tough it out. Eventually caught in the toils they had woven for themselves, they turned and ran, abandoning their accomplices to face the music alone. Greater men would have managed defeat with greater dignity and greater moral, even physical courage.

Mr. Saikal and Mr. Horeyda are agreed on certain key points. These incudes: (1) the need felt by the young Shah at the end of World War II to prove himself and so live down the fact that he had been put on the throne by the British and the Russians; (2) the later need to prove himself after the Mossadeq interlude in the early 1950s and so live down the fact that he had been returned to his throne in 1953 by the Americans; (3) the Shah's key mistake, after the 1973-74 oil crisis, of getting every extra cent (and more) as it came in; (4) the disastrous effect of the blank check reportedly given the Shah by President Nixon and Secretary of State Kssinger for the acquisition of the most sophisticated US weaponry -- which a population still at least 50 percent illiterate could not either use or service property; (5) the Shah's obtuseness in failing to recognize that it was folly to ignore the internal political imperatives in a society subject to such forced rapid change.

Both books have much to be said for them -- with Mr. Saikal's being the move valuable as a volume of reference. Mr. Hoveyda has a tendency to quote unsubstantiated report for rumor -- albeit identifying it as such. Yet the definitive and comprehensive story of the drama which engulfed Iran from the early 197