Sometimes when you’re trying to read a book by a writer from every country in the world, you have to travel in time as well as space. While there may not be any translated literature from that nation available in print at the time you’re looking, if you dig back into the past you can occasionally get your hands on an edition of a translation published decades ago that will take you into an imaginary universe from which you would otherwise be shut out. These out-of-print books are like portals, opening and closing  at will: not everyone can get to them, they pop up in surprising settings and you’ll rarely find one in the same place twice.

My Paraguayan pick was one of these books. As far as I can find out, there is little other than Helen Lane’s 1986 translation of Augustos Roa Bastos’s I The Supreme out there for us English-language readers (do tell me if you know differently). Luckily, I was able to get hold of a faded 1988 edition listed by an independent bookseller on Abe Books (there are a few others on there at the moment, but they may disappear at any time).

The 1974 novel, which saw Bastos permanently exiled from his homeland, is a fictional rendering of the recollections, pronouncements and paranoid fantasies of the early 19th century Paraguayan dictator Dr José Gaspar Rodríguez de Francia (who dubbed himself El Supremo). Constructed by an anonymous compiler from a mountain of charred dossiers, pamphlets, correspondence and other documents salvaged from a fire at the time of the ruler’s death, the narrative presents a mind turning in on itself as the tyrant confronts his own mortality.

From the first page – which displays a lampoon in the voice of El Supremo found nailed to the cathedral doors in the capital – the text babbles with questions about identity, authority and authorship. The novel is shot through with footnotes and extracts from other works that contradict the primary account, as well as revisions from the tyrant as he creates his own account of the founding of the Perpetual Dictatorship. As El Supremo’s shadowy scribe puts it, in this world of reconfigurations, suppressed voices and fabrications, ‘even the truth appears to be a lie’.

For all the slipperiness of the narrative, however, the character of El Supremo looms large, riddled with the conflicts, eccentricities and the lack of empathy that comes from years of being cut off from normal human interaction. Bastos’s portrait of the ruler’s paranoia, who sees himself surrounded by people with ‘a bad case of the itch to be kings’, is brilliant and points up the psychology behind the grotesque and brutal punishments he metes out as casually as he orders his food – the cells blocked up to admit no light, the traitors left sitting in the sun, the man forced to row until he dies. These are offset by El Supremo’s delusions about his own benevolence, reflected in outbursts of irrational generosity – as in the case of the meticulous list of toys he orders to be distributed to children at Epiphany.

Bastos’s greatest achievement, however, is that, while revealing the monstrous actions and self-deception of the tyrant, he brings out his humanity too. This comes through in the lonely, sober tone of many of the entries in El Supremo’s private notebook, as well as through glimpses of the ruler as a frail old man playing dice in his slippers and contemplating the impending loss of his faculties. It also lives in his flashes of insight into his situation and his wistful daydreams about how if he had met a woman and had a family he might have enjoyed a peaceful, quiet old age, rather than sitting in fear and isolation, thinking about crowds burning his effigy and listening to ‘the sounds of a sick mind clattering along’.

For all its brilliance, however, the novel does come with a health warning: its dense, heavy style will be too rich for some appetites. The concentration wanders in its maze of associations and you sometimes have to retrace your steps to pick up the thread again. Although Bernard Levin might have read it twice in a weekend – as he writes breezily on the back cover – the book will take most people much longer to get through (I had to allow four days).

If you stick with it, however, the rewards are great. The I the Supreme is many things: a portrayal of the nightmare of being able to trust no-one but yourself; a portrait of a mind hemmed in; and a reminder of how easily we might be other than we are. Extraordinary.

I the Supreme (Yo el Supremo) by Augusto Roa Bastos, translated from the Spanish by Helen R Lane (Faber & Faber, 1988)