Gave it to my nephew when he told me history was boring. He came back two days later, furious.

It's shelved in science fiction and there's no science in it. No machine, no explanation, no theory of time. Dana is in her flat in 1976 and then she's in Maryland in 1815 — and Butler refuses all the way through to tell you how. That refusal is the most confident decision in the book, because the moment you explain it you have written a different and considerably worse novel.

What it actually is: a novel about how fast a person adapts. Dana arrives with a modern woman's certainty and within a few trips she is calculating, managing, keeping her head down, learning which cruelties can be survived and which ones cannot be argued with. The horror isn't the whip. It's the speed of the adjustment.

Rufus is the achievement. Butler could have made him a monster and instead made him a boy who is sometimes decent, who genuinely needs her, and who is being shaped year by year by a system that rewards the worst thing in him. Every time you're ready to write him off he does something human. Every time you soften he does something unforgivable.

Kevin gets less attention than he deserves: a white husband stranded in that period, and what five years of it does to somebody who was certain of his own decency.

It opens with her in a hospital bed with an arm gone, and everything afterwards is paid for in the same currency.

Nine. It's been adapted twice and neither version is close, so skip those; the graphic novel version is decent if you want it in that form.