After visiting the India of the thirteenth century with Marco Polo, the next Penguin Little Black Classic takes us back by twelve centuries and to another part of the world. Number 17 is Suetonius’s biography of Caligula, taken from The Twelve Caesars.

Suetonius begins his Twelve Caesars with Julius Caesar, followed by Augustus and Tiberius. Caligula or Gaius, as Suetonius usually calls him, is the fourth life in the sequence.

And it is a fascinating read.

The biography seemed to unfold for me in three parts. The first introduces us to Caligula’s family and childhood, and while reading it, I found myself forming a surprisingly favourable impression of the boy who would become emperor.

Gaius was the son of Germanicus, an illustrious Roman general who was loved across the Empire. The young Gaius was much loved as well. Even the name by which history remembers him began as an affectionate nickname. As a child, he dressed as a soldier and wore miniature military boots. The soldiers called him Caligula: “little boots.”

His father was expected to have a great future but died while Gaius was still young. According to Suetonius, Germanicus was poisoned. He even gives us a wonderfully strange detail: after Germanicus’s body was cremated, his heart was found intact. And in those days, people believed that a poisoned heart could not be destroyed by fire.

It is exactly the sort of detail that makes Suetonius such entertaining company.

The second part concerns the death of Tiberius and Caligula’s accession. And for a while, the favourable impression continues.

Rome rejoices at its new emperor. Caligula distributes money, undertakes public works, begins the construction of aqueducts and stages lavish public entertainments. Suetonius says that in less than three months, 160,000 victims were sacrificed in celebration of his accession.

I stopped at that number. 160,000 human sacrifices? See, it’s easy to confuse. Victims for me means people. Fortunately, no. “Victims” here means sacrificial animals. Even so, the sheer number gives some idea of the extraordinary enthusiasm with which Rome greeted its new emperor.

And then Suetonius turns the knife.

The third and longest part of the biography presents us with an altogether different Caligula. He becomes cruel, unpredictable and increasingly deranged. People can be killed almost on a whim, and nobody seems entirely certain what might provoke him.

Suetonius reports that Caligula had incestuous relationships with his sisters. He was supposedly particularly attached to Drusilla, whom he married to Lepidus while continuing his own relationship with her.

Then there is his famous horse, Incitatus. Caligula lavished extraordinary attention on him and, according to Suetonius, even intended to make him consul.

Caligula also loved performances. He participated in gladiatorial contests and enjoyed singing and dancing himself. Unfortunately, attending a performance in his company appears to have been a rather hazardous experience. React to something in a way the emperor disliked and you might find yourself punished, or even thrown into the arena.

Imagine having to watch a play while simultaneously keeping an eye on Caligula to make sure you were laughing at the correct moments.

Suetonius also writes about Caligula’s terrible insomnia. He supposedly slept no more than three hours a night and spent much of the remaining time wandering through the palace. Suetonius describes him as both physically and mentally disturbed, and the portrait becomes increasingly grotesque as the biography continues.

The third section is filled with accounts of Caligula’s cruelty, sexual excesses, humiliations of others and increasingly bizarre behaviour.

And while reading this section I started to wonder, how much of this should we believe? Suetonius wasn’t there.

Suetonius was born decades after Caligula’s death. He had access to records, but he also relied on stories, rumours and anecdotes that had accumulated around the emperor. And when almost every story about a man makes him appear more depraved than the one before it, a little caution seems sensible.

There aren’t many surviving contemporary sources that allow us to reconstruct Caligula independently in any great detail. So Suetonius remains enormously important. But perhaps he shouldn’t always be read like the newspaper of record.

Sometimes it is better to approach him as an exceptionally well-informed Roman tabloid. And what a tabloid.

I began this little volume knowing Caligula mostly by reputation. Suetonius gave me the affectionate little boy in military boots, the young emperor welcomed joyfully by Rome, and then the monster whose name survived two thousand years.

How much of that monster was Caligula and how much was the story Rome subsequently told about him, I don’t know. But this particular Roman tabloid was entertaining enough that I now want to read about the other eleven Caesars.