Adam Roberts is the master of the big idea; of high-concept science fiction.
He is rare in the genre for eschewing series of recurring characters and worlds, and instead writing one-off books in which he takes an idea, batters it senseless until it is bloody, beaten and unusable by any other writer, and leaves his readers in a state of stunned shock. But however high the concepts he makes his own, they are never at the expense of character, and in By Light Alone, like all of Roberts' recent works, the people make the big ideas leap off the page.
The central conceit is that, a century or so hence, hunger has been eradicated thanks to a treatment that allows human beings to absorb, through their hair, all of the nutrients that they need from sunlight. People can live by light alone.
But rather than ushering in a utopian golden age, this scientific leap has served only to widen the gulf between the rich and the poor. The wealthy elect not to have the treatment, and take pride in old-fashioned eating, so that in a neat reversal of contemporary mores, the dirt-poor are as thin as rakes because they don't consume unnecessary fat, and the fashionable mark of wealth is to be podgy.
No longer having to service the starving masses of the third world, the rich have got richer. From the book's Art Deco cover onward, we are introduced to a Second Jazz Age which is under way in the wealthy West, whose indolent moneyed citizens have languid, meaningless affairs while drinking their way around the world.
In the first section, we are given a view of this world from rich George Denoone, a sympathetic character who is plunged into a nightmare when his young daughter is kidnapped during the family's skiing holiday.
So skilfully has Roberts painted the novel's Gatsby-esque world, that it is a shock when he reveals the flipside and we follow a Messianic young girl on her journey across the poor nations – and into a shocking collision with George's family.
If By Light Alone were written by David Mitchell or Margaret Atwood, for example, it would doubtless be said to "transcend its science fiction" roots, as all literary fiction which borrows SF trappings must. But By Light Alone is unashamedly SF, and would that half the supposed "literary" novels on the shelves today were as well written, thoughtful and intelligent as this.