As we learned from the Millennium Bug, a single digit can cause potential havoc with a complex, number-based system. Yoon Ha Lee brilliantly extrapolates this contemporary reality in science-fictional terms by depicting a densely hierarchical civilisation that spans thousands of star systems, all in thrall to ‘the calendar’, an agreed system of ethical, scientific and even conceptual management whose adherence is enforced with fundamentalist religious fervour. Even the exotic effects that power star drives and weapons – such as the wonderful calendrical sword, which is like a lightsabre but with numbers instead of light – must all align, or they simply will not work.

Revenant Gun is Book Three in the author’s Machinery of Empire trilogy, and portrays two characters following the overthrow of the high calendar and the establishment of alternative, conflicting societies. The protagonists are Jadeo, the Hannibal Lecter-type dark genius reactivated to win a war in Book One Ninefox Gambit by ambitious space captain Cheris – who is now trying to assassinate him. Interestingly, Cheris still has a big chunk of Jadeo’s memories – indeed, my issue with the first book was that a new character dominates the last third of the story – while the ‘new’ Jadeo has the rest. But is the new Jadeo who and what he appears to be?

The first third of the book is a careful establishment of the state of play, with much detail accorded to rituals such as food and the wearing of gloves, that ground proceedings in a recognisable, albeit left-field way. Only the author’s linguistic and world-building skills keep you engaged during these sequences – and then it kicks off. Yoon Ha Lee turns everything he has established on its head in a bravura display of high-concept, empathetic, character-driven SF, with reversals and revelations that have you thinking in his language even when you aren’t reading the book. This is my favourite 2019 space opera, because having read it I barely remember the others.