The centrepiece of this heartstopping book is some breathtakingly savage and brutal worldbuilding - a land constantly on the edge of catastrophe, constantly in waiting for the next apocalypse as geological instability leads to massive eruptions and quakes with attendant disastrous aftereffects - tsunamis, endless winters, famines etcetera. Civilisations and societies routinely break down and humanity struggles to survive and rebuild while trying to prepare for the next big blow. The Sanzed Empire has survived for several cycles now, largely because it has corralled and controlled the Orogenes, individuals with the ability to control kinetic and seismic energy, who can quell or cause quakes and whose full range of powers and abilities remain mysterious and untapped, largely through systematic demonisation and indoctrination. Imperial Orogenes are policed by a ruthless and powerful group called the Guardians.

The set-up is brutal, the society it creates is functional, thriving, even admirable, filled as it is with practices and norms that seem appalling (and yet not completely unfamiliar) to us. The book opens just as it all comes to an end, and in a terrible act of destruction, a massive rift is opened, triggering the downfall of the Empire and the start of a possibly final Fifth Season. It also starts with a smaller act of horror, as Essun, an Orogene in hiding in a small rural town, mourns the murder of her son by his father, and the taking of her daughter. While ash starts to fall, she pursues her husband and daughter through the slowly building chaos of a society starting to break down.

There is very little about this book that is not compelling, awe-inspiring, epic and jaw-dropping. It is also terrifying, horrifying and filled with pain, tragedy, guilt and injustice, yet it is told in a uniquely readable and engaging voice - people cope, adapt, survive, move on as best they can. It is not so much about the triumph of hope, too early in the trilogy to say that and it seems unlikely to be about anything so facile, but it is about bullishly continuing to exist in the face of a world that is constantly trying to wipe you out, and the cost of that survival.