THE EXPULSION of more than a million undocumented foreign workers from Nigeria in January was one of those events that periodically startle Americans. Suddenly we realize that while we are figuring out whether to deploy the MX missile, how to save the Social Security system, and when to begin the 1984 presidential campaign in earnest, compelling human, political, and economic dramas are taking place elsewhere in the world. And we have little notion of their importance or their impact.

In this case newspapers, magazines, radio, and television did their best to convey the enormity and explain the significance of this exodus, one of the largest forced migrations of people in Africa in the last century. Out came the dusty maps, and even if a few countries were mislabeled along the way, the public was reminded of some basic facts: Nigeria, one of the main beneficiaries of the dramatic rise in oil prices during the 1970s, is now facing catastrophe as a result of the steep decline in those prices. Ghana, where most of the expelled workers came from and would now return, is no longer the proud African leader that it was at independence in 1957, but an economic basket case. These are countries that matter to the United States, if only because Nigeria has until recently been this country's second largest foreign supplier of crude oil and because Ghana is in the midst of a political crisis that has made it acutely vulnerable to the blandishments of Libya.

But, understandably distracted by more immediate concerns, Americans turn their attention quickly away from the tragic events along the West African coast. The fact that Ghana's poopulation increased by 10 percent overnight does not really mean very much from afar. Nor is it easy to identify with the fact that Nigeria is about to test its American-style constitution and hold a civilian presidental election for only the second time.

David Lamb is one of the American journalists who has tried to do something about his countrymen's tradtional lack of interest in Africa. Based in Nairobi for four years, he carried on the long and distinguished reputation of the Los Angeles Times for serious reportage from Africa. Many of his stories were so good that it was a shame they were not read by a wider audience; some were classics. The Africans in a compilation of those stores, plus a lot of other things that Lamb found in his notebooks (3,200 pages worth, he tells us).

Organized thematically, the book is a grand sweep around the African continent, a catalogue of how much is wrong and how little is right and why. The publisher is encouraging comparisons with John Gunther's Inside Africa, published in 1953, a grander and more eccentric travelogue that contained a great deal of information and (people tend to forget) quite a few wrong predications. These are some parallels. Lamb even emulates Gunther by pausing frequently in mid-passage to offer the reader little one- or two-paragraph editorials about what needs to be done to improve the situation under discussion. They are well-intentioned, but often more distracting than enlightening.

At its best, however, Lamb's narrative is very good indeed. His account of the ruin of Uganda is excellent, because he not only recounts how the monstrous Idi Amin stayed in power (with the cynical help of the Palestine Liberation Organization and other idealistic groups), but he also explodes some of the myths about Amin's predecessor and eventual successor, Milton Obote, whose reputation far exceeds his performance. When Lamb turns his meticulous reportorial eye to some of Africa's tinier countries, such as Guinea-Bissau and the island nations of the Comoros and the Seychelles, the results are insightful, revealing, and often sadly humorous. His account of a visit to the Ogaden Desert where Ethiopians and Somalis have been fighting each other for centuries, is vivid and chilling.Lamb also zeroes in on the worst examples of hypocrisy in black-ruled Africa and speaks eloquently of the need for population control, better education, and more basic medical care.

But in some instances, Lamb's account is selective or simply misleading. To be sure, there has been far too much sentimental coverage of Africa over the years by specialists who are overly concerned with maintaining their access and pleasing their subjects; Lamb's solution to that problem often seems to be a blend of negativity and naivete.

Yes, President Albert-Bernard Bongo of Gadon changed his name to El Hadj Omar Bongo, but not, as Lamb suggests, just because this would sound "more African" -- rather because he was playing on his status as a Moselm, and the use of "El Hadj" indicates that he has made the pilgrimage to Mecca. It is true that witchcraft is still practiced in the tiny West African nation of Benin, as in many other places, but it is also true that Beninois intellectuals have played an important role in universities and other institutions thoughout West Africa. It is unfortunate to be told the former without also being told the latter. Of course Africans sometimes spend hours in a line and finally go away without the thing they have been waiting for, but has Lamb ever taken a look at the lines of a big-city unemployment office in the United States?

Lamb purports to feel an affection, an "exhilaration" for Africa. But what gradually emerges from his book is a modern and more sophisticated variation of the nostalgic contempt that was so often expressed by missionaries and colonial administrators half a century or more ago. "Below the paper-thin veneer of civilization in Africa lurks a savagery that waits like a caged lion for an opportunity to spring," he says at one point, having just discussed the 1980 coup in Liberia. His Africa is a place of promiscuity. ("Where a European couple might kiss, Africans copulate.") Entire tribes are written off as disinterested in education and useful only as soldiers. The explanation for car accidents among Kenyans and black South Africans is that "an African does not conceptualize a potential problem the way a Westerner does." And Lamb finally found that an African will rarely "reveal his inner emotions or talk about his beliefs in more than superficial terms." These are very tired stereotypes, and it is a shame to see them given new life.

As if to be balanced, Lamb also uses broad and unfair generalizations to portray the white people of South Africa (a country that gets only cursory attention at the end of his bood). "Talking race with an Afrikaner is like discussing mathematics with a stone wall," he tells us; "the Africaner tends to be humorless, stern and pious. He would not, I suspect, look misdressed in a Nazi storm-tropper uniform." Lamb's heroes are the English-speaking white South Africans. But anyone who has gone beyond the old slogans knows that there is great and growing diversity of opinion within the Afrikaner community, that some Afrikaners have been banned or imprisoned for their views and actions, and that the English-speaking community has become increasingly reticent and (in the view of some) irrelevant to the formulation of South Africa's political future.

Slurs and simplifications aside, Lamb also reaches some disappointing conclusions. Benign dictators may be the best bet for now, he says, and the West must pour financial assistance into their countries, "even if much of that money is filtered off by corrupt presidents and ill-conceived projects." And we must continue to provide guns, "even if some of those guns are used by despotic presidents to perpetuate their own rule. The alternative is to let Moscow take Africa piece by piece."

Moscow is not taking Africa piece by piece, as Lamb amply demonstrates elsewhere in his book, and a creative American foreign policy in Africa includes many more subtle alternatives than the indiscriminate care and feeding of unpopular dictators.