Jack Campbell’s military science fiction series reaches its penultimate instalment in Relentless. The book opens with an account of Captain John Geary’s courageous and legend-making battle that started the galactic war the books describe over one hundred years ago, that has been referred to frequently throughout the previous four books, but never given a full description. Here, we get to read of the fraught battle and of Geary’s rescue from hibernation sleep a century later.

The book is much the same as its predecessors: politics, tactics, conspiracies and an unspoken romance bridge the gaps between large scale space battles. It’s perhaps unlikely to change anyone’s world, but fans of the series will be eager to catch another dose of Campbell’s moreish prose, before the grand conclusion in the final novel.

Relentless also features a ground battle, another first for the series, in which POWs are rescued,...