Sally Gardner has been absent from the middle-years lists for some time, too. Although not quite as much of a household name, the prize-winning Gardner is another dab hand at literary world-creation. Fourteen years have passed since Gardner’s last middle-years novel, I Coriander, and her latest, Invisible in a Bright Light, is set in a Copenhagen theatre full of backstage drama. Her assured plot swings audaciously between alternate realities, as another pair of twins, Maria and Celeste, are forced to play a confounding, dangerous dream-game: the Reckoning. The prize is the lives of their parents, and the lives of the rest of the passengers of a ship that might, or might not, have been lost at sea in the Baltic in 1870.