Born in obscurity, frustrated in youth, the dictator rises through accident, patronage or anything except merit to blossom into a fully fledged evil-doer, desperate for the respect and admiration that are wrung from the populace only by skilled PR manipulation. Often feigning modesty, he soon generates a cult that he personally develops. Women and even brave men feel overcome in his presence; schoolchildren chant the praise of the father of the nation; artists and writers deify the great leader. Dictators generally come equipped with an ideology, but since they have no principles, only a lust for power, the process of propagation turns it into a mockery.

Although dictators often fancy themselves as writers or philosophers, they fail to make the grade as intellectuals, and the Little Red Books they produce are travesties. If they are dictators of the left, their attempts at radical reform bring famine and suffering to the population. If dictators of the right, they go to war, with the same consequence of popular suffering, and lead the nation to shameful defeat. They long to be popular, and put great effort into creating that illusion, but it is all fakery. Surrounded by sycophants, they are friendless, lonely and paranoid. Most of them die a dog’s death, but if they somehow manage to avoid this, people only pretend to mourn them. After their death, they are quickly forgotten.

This is the collective portrait that emerges from Frank Dikötter’s book, the eight chapters of which deal with Mussolini, Hitler, Stalin, Mao Zedong, Kim Il-sung, Haiti’s “Papa Doc” Duvalier, Romania’s Nicolae Ceauşescu and Ethiopia’s Mengistu Haile Mariam. Despite their fundamental similarities, his dictators do have stylistic differences. Stalin allowed streets and cities to be named after him, while Mao did not. Hitler was a teetotaller and Duvalier a follower of the occult. Kim’s floodlit statue towered over Pyongyang, following the tradition of Stalin statues, but Hitler vetoed the construction of statues of himself (thinking this honour should be reserved for great historical figures), and Ceauşescu and Duvalier felt the same. Some dictators’ enforcers wore brown shirts, others black, and still others had no uniform. Mussolini and Hitler excelled as orators, while Stalin was an undistinguished speaker who never addressed mass rallies. Stalin, Mao and Duvalier wrote poetry, Hitler painted and Mussolini played the violin.

Duvalier modelled himself on Baron Samedi, the Vodou spirit of the dead and guardian of cemeteries

In the chapters on the “big” dictators – Mussolini, Hitler, Stalin and Mao – Dikötter dwells on the cult that developed round them. All of them headed a party that borrowed some of their charisma, and their regimes featured a variety of secret police and enforcers as well as cheerleaders and informers. Ordinary people were encouraged to believe that anything bad was done by subordinates without the dictator’s knowledge (“If only the Duce/Fūhrer/vozhd’ knew”). In fact, the dictators repeatedly made terrible mistakes and appear to have had few if any lasting achievements. With Mao and Stalin, the “dog’s death” trope doesn’t quite fit, but Dikötter runs a modified form of it anyway. Dying, Stalin lay unattended, “soaked in his own urine”, and “one month after his funeral”, his “name vanished from the newspapers”.

Dikötter’s sources are impressive, including 16 archives from nine countries, one of them being the former Soviet Central Party Archive (now renamed RGASPI) in Moscow. Despite this, I did not find the Stalin chapter particularly compelling, no doubt partly because I do not share the author’s view that the cult is the most interesting thing about Stalin. When Dikötter writes that the dry-as-dust Short Course on the History of the All-Union Communist Party, in whose composition Stalin participated, “deified Stalin as the living fount of wisdom”, I wonder if he has actually read it.

For me, the most entertaining chapters of this book were about the dictators I was least familiar with. It is intriguing to read that the remains of Mengistu’s predecessor, Emperor Haile Selassie, were possibly “buried underneath his office, placing his desk right above the corpse”. The stand-out dictator, in terms of entertainment value, is Duvalier, with his personal militia the Tonton Macoutes, who “dressed like gangsters, with shiny blue-serge suits, dark, steel-rimmed glasses and grey homburg hats” for their enforcement duties. Duvalier modelled himself on Baron Samedi, the Vodou spirit of the dead and guardian of cemeteries, and sometimes dressed the part, all in black, with top hat and carrying a cane. Dikötter characterises him as a “dictator’s dictator”, by which I think he means the stripped-down model with “no true party” and without the “pretence of ideology”. Certainly Duvalier has a claim to be the reductio ad absurdum.

He is one of two dictators in the book with dynastic ambitions for their sons, the other – and more successful over the long term – being Kim. That seems to me an important difference from the others, including all the “big” ones, but Dikötter does not remark on it. Overall, his argument is that dictators’ cults are not peripheral phenomena but lie “at the very heart of tyranny”. He holds that, contrary to widespread belief, the dictators had not “captured the souls of their subjects and … cast a spell on them”. “There never was a spell. There was fear, and when it evaporated the entire edifice collapsed.” This seems a strange conclusion when it comes to Stalin, whose successors wrestled with his legacy for decades, and an even stranger one for Mao, the dictator closest to Dikötter own field of expertise. But denying any contemporary popularity or lasting impact to the dictators seems to be the main point of the book.

While Dikötter is explicitly dealing with 20th-century dictators, the stage is set in the preface by France’s 18th-century Sun King, Louis XIV, a great practitioner of political theatre, remembered for his aphorism “L’État, c’est moi”. But if Louis was a model for any of the 20th-century dictators, we don’t hear of it in this book. For that matter we learn little about whom the dictators modelled themselves on (or against) and how they reacted to each other. Yet surely Mussolini, Hitler and Stalin kept an interested eye on each other’s PR practices and on occasion quietly imitated them; and Mao was scarcely indifferent to Stalin’s example.

Questions of chronology, sequence and influence are not much discussed here. The mid 20th century is generally considered the heyday of dictators of the right and the left, but Dikötter does not explore why this might have been so, and even obscures the issue by including chronological outliers such as Mengistu. It is important to study dictators, he suggests, because they are an eternal threat to democracy and freedom – but not, it seems an acute current threat. “Dictators today, with the exception of Kim Jong-un, are a long way from instilling the fear their predecessors inflicted on their population at the height of the twentieth century … Even a modicum of historical perspective indicates that today dictatorship is on the decline.” That’s reassuring. Perhaps it would be churlish to ask how we got so lucky.

• How to Be a Dictator is published by Bloomsbury (£25). To order a copy go to guardianbookshop.com or call 020-3176 3837. Free UK p&p over £15, online orders only. Phone orders min p&p of £1.99.