The greatness of this book lies in its novel mechanics of time travel, its structure, its setpieces, its mixture of alternate history and time travel, its poignancy and paradoxes, and the fate of a heroine whose voice is so appealing.

The titular game, named after a real 15th century ecclesiastical Nicolaus Cusanus who plays an important part in the story, is the organizing metaphor for the novel’s structure and the suggestive counterpoint for the journey of Domenica, a botanist who narrates most of the book. It’s a game where modified balls are thrown at a target, no game or moment in time is ever the same, and indirection is a strategy, patience a necessity.

And so it is with the opening of this book, a prologue that starts out like some tale of time travelers confronting medieval primitives, but it’s really just Europeans coming out from behind the walls (figurative and literal) they’ve built to keep hordes of refugees, fleeing climate change, from moving into northern Europe. And it’s not like there’s as much room as there used to be on the continent. A large swatch of Germany has been rendered uninhabitable by plutonium poisoning.

Patience is needed for the first 100 or so pages as Domenica is introduced, her voice leisurely giving us a travelogue of a violent Rome of the mid-21st century, a city plagued, by other things, feral talking dogs, weapons of war abandoned. And then the pace picks up as Domenica is recruited into a secret Vatican project to travel back in time to get genetic samples of extinct flora. Foreshadowing obvious and not so obvious is rife as early sections have Cusanus ominously speaking of a strange woman about to be burned as a witch.

Jeschke’s time travelers are memorably compared to “dogs on a subway”. They have little idea how their time travel system works or who built it or why, indeed little beyond some basic features they can exploit. Jeschke cleverly uses not only standard scenes of dialogue to explain things but epigraphs from cosmologists and artificial intelligence researchers like Albert Einstein and John Wheeler and David Deutsch and Cusanus himself to rationalize by suggestive speculation.

The plot, like the balls of Cusanus’ game, veers all around. Poignancy and suspense can quickly change to farce. Long travelogue sections suddenly become quick cut scenes of impending doom as Domenica goes on missions into time with both professional and personal ends. Why time travel dooms romance among its practioneers is laid out.

Some set pieces aren’t strictly necessary. A frail old woman tells how she alone survived years of isolation in space after a doomed Mars mission. Wheelchair bound veterans battle youths in Amsterdam street riots. But I enjoyed them as well as Jeschke’s extended extrapolations of virtual reality and nanotechnology.

In the middle of the book, is a chapter called “The Cusan Acceleratio”and previously published as a short. It’s a quite detailed timeline of an alternate history and integral to the book. It’s also understandable to see why Jeschke says it was the most difficult section to write.

Not so integral to the plot are the several almost identical scenes with Cusanus. I understand the purpose: to show how alterations in timelines affect Cusanus. However, I think they could have been shortened, and that was the book’s only flaw for me besides some predictable German phobias about nuclear power.

The ending is powerful and unexpected. The narrative stops in quite an unpredictable place. ( )

Une approche intéressante du voyage dans le temps et des univers multiples. ( )

An elaborated time travel story with a pinch of postapocalyptic and paralell universe vision. One of the best time travel theory I've ever read (perhaps after Asimov's). Jeschke at his best. A must read for every hard SF fan! ( )