‘Emperor of Rome: Ruling the Ancient World’
By Mary Beard
Liveright, 512 pages

‘Big Caesars and Little Caesars: How They Rise and How They Fall—from Julius Caesar to Boris Johnson’
By Ferdinand Mount
Bloomsbury Continuum, 304 pages

There are lots of Roman emperors to cover in a book about an empire that took in a lot of territory, but Mary Beard helps us out with several maps and a list of main characters in different dynasties and civil wars, as well as a timeline and a section on further reading and places to visit.

Readers familiar with Ms. Beard know this will not be dry history, so it is not surprising that in her “Welcome,” she announces she will deal with “day-to-day practicalities” of emperors’ lives: “What, and where, did they eat? Who did they sleep with? How did they travel?” She also sees history and biography from the ground up, from the perspective of “enslaved cooks, diligent secretaries, court jesters—even a doctor who treated one young prince for tonsillitis.”

Ms. Beard explores what it “meant to be a Roman emperor,” noting that after Augustus the size and shape of the empire did not change too much and that it was “administered in more or less the same way” for 250 years.

I was hoping she might stray into contemporary history, as Ferdinand Mount does, in his chapters on Boris Johnson and Donald Trump, especially since comparisons between America and the Roman Empire have been made by writers as different as Sylvia Plath and Gore Vidal, both of whom had a significant interest in the ancient world.

Mr. Mount begins his prologue: “Caesars are back, big Caesars and little Caesars, in big countries and little countries, in advanced nations and backward nations.” Not only has liberal democracy not triumphed since the defeat of fascism and communism, but the possibility that any society may succumb to Caesarism is, well, very real, Mr. Mount avers.

You may be tempted, as I was, to turn to the chapter on Mr. Trump to see how he fits in. Mr. Mount is careful to show that in only two vital respects is Mr. Trump’s election and government truly unprecedented. Nothing new about Mr. Trump’s nativism and nationalism and isolationism, Mr. Mount notes, referring to Charles Lindbergh, William Randolph Hearst, and David Duke — who have all proclaimed “America First.”

The tendency to close the door on immigration is certainly not new. One renowned diplomat, George F. Kennan, “warned against recklessly trashing American culture ‘in favour of a polyglot mismash,’” Mr. Mount points out. Mr. Trump’s nationalism is just more “shouty” and he puts his points “more roughly.”

What Mr. Mount finds most disturbing and Caesar-like in Mr. Trump is the “contempt for elected representatives.” Too many of them to remember or deal with, Mr. Trump has said. What is “new, odd, even unique, in American history about the Trump experience and the Trump presidency” is his “relentless non-stop campaigning and his chaotic style of government.”

Instead of the “Deep State,” Mr. Trump operates in the “Shallow State,” Mr. Mount argues, which produces anarchy and lack of interest in governing. Here is Mr. Mount’s Shakespearean dismissal: “The Shallow State is insistently self-important; it struts and frets its hour upon the stage, impatient and resentful of competition or critique.” What will save the day, in Mr. Mount’s view, is democratic institutions that can slowly and inefficiently, and yet relentlessly, check Caesarism.

There are surprisingly few references to Caesars in Mr. Mount’s Trump chapter. Perhaps we are meant to see for ourselves the parallels, though I hanker for Mary Beard to step in and provide another map of contemporary Caesarism. 

I take exception to some of Mr. Mount’s asides. A Labour cabinet minister, Michael Foot, did not defend Indira Gandhi’s temporary dictatorship because he took a neo-colonial view that “Indians didn’t really need all that stuff like habeas corpus and freedom of speech.” I decided after talking to Foot that he simply trusted Gandhi as a friend who gave him certain assurances — and that is perhaps another way of condoning Caesarism and its power because of the personalities involved.

Mr. Rollyson is the author of “A Private Life of Michael Foot” and is at work on “Making the American Presidency: How Biographers Shape History.”