Leopold’s dynastic rule could not last. In 1908 Belgium assumed full responsibility. The Belgian Congo was racist, objectionable in its inequity and plunder. Colonial officers and particularly commercial officers were skittish; tiny numbers held the enterprise together. Yet many older Congolese today remain wistful for it. Compared with what followed, the colony was in some ways admirable. Mortality fell, education rose. A large chunk of the colonial budget was locally raised. Working conditions became better than in most other places in Africa. A gold miner in the Kilo-Moto mines, for instance, received a daily ration of meat or fish, beans, rice, bananas, salt and oil — a diet many Congolese today can only dream of.

Congo had a good Second World War. The colony was manful where the mother country folded. Congolese troops helped liberate Abyssinia (now Ethiopia). The managing director of the state mining concern flooded the uranium mines at Shinkolobwe and shipped 1,375 tons of uranium to New York, a stockpile that enabled the Manhattan Project. The postwar period was curiously calm. Whites and a very few educated Congolese lived sunny lives in the highly socially engineered campuses around the country’s larger enterprises. In 1955, King Baudouin was rapturously received right across Congo. But back in Belgium an obscure article in a Flemish Catholic workers’ magazine suggested Congo should become independent in the year 1985. The article was a sensation in Congo. It was the first time a date had been mentioned: Independence was suddenly not a matter of if, but when.

As late as 1959, the handover still looked years away: “Of the 4,878 higher-­ranking positions, only three were occupied by Congolese in 1959.” That explained the desire for independence, but also showed how unprepared the country was. Independence came on June 30, 1960 — so fast, like a craft careening over a waterfall. The Congolese Army under the command of Gen. Émile Janssens, “the most Prussian of all Belgian officers,” collapsed after only a few days. If it had remained under external command for another four years or so, while Congolese staff officers were trained in Belgium, it might have been of service to the country. As it was, angry corporals became greedy colonels overnight. Most of the Belgians left within weeks.

There were four Congolese leaders — Joseph Kasavubu, Moïse Tshombe, Patrice Lumumba and Mobutu — who triumphed. Lumumba was canonized as a peerless anticolonialist by Pan-­Africanists after being executed by Tshombe, with Mobutu’s connivance. Van Rey­brouck quotes Congolese and Belgians as saying that Lumumba was vain, weak and empty-headed. His possible turn toward the Soviet Union and determination to keep Congo as a centralized unitary state meant there was C.I.A., MI6 and Belgian intelligence collusion in his death.

Alas, there is no space here to go into Van Reybrouck’s treatment of the presidency of Kasavubu, the early Mobutu years, the rotting out of the state, the horrors of the first and second Congolese wars, the entry of China into Congo. Nor can justice be done to the numerous personal stories of Congolese that Van Rey­brouck tells. I will pick out just two.

Simon Kimbangu was born in 1889. He believed himself to be a divine messenger of Christ. He saw visions. Kimbanguists to this day believe he raised the dead. He said, “The whites shall be black and the black shall be whites.” The Belgians did not like that. Kimbangu was sent to prison in 1921 and died there in 1951. He’s important because he pioneered the mix of populism and Pentecostalist fervor that is arguably the strongest social force in Africa. With its large numbers of unemployed youth, new divines are sure to rise up in Congo. These Kimbangus will most likely be more violent and explosive — a kind of counterreformation against secularism, science and individualism.

Finally, Van Reybrouck offers one of the most extraordinary African stories I have come across in recent years. He sought out elderly Congolese to get their memories. That was how he met Étienne Nkasi in a shack in Kinshasa. Van Reybrouck went into the dimness and was greeted with a Roald Dahl scene. Nkasi sat up in bed. “His glasses were attached to his head with a rubber band. Behind the thick and badly scratched lenses I made out a pair of watery eyes.” How old was he? “Je suis né en mille-huit cent quatre-vingt deux.” I was born in 1882. A 126-year-old man, one of the oldest men who ever lived? Born three years before King Leopold took control of Congo? Van Reybrouck checked and double-checked. Nkasi knew the names of missionaries apparently held only on records in Belgium. He personally knew Kimbangu, who was born in a nearby village. “Kimbangu was greater than me in pouvoir de Dieu, but I was greater in years.” Nkasi died in 2010, aged 128. Van Reybrouck says he met Nkasi for the first time right after Barack Obama won the presidency. “Is it true,” Nkasi asked in wonderment, “that a black man has been elected president of the United States?”