The girl on the front of this vintage young adult book from 1988 ‘The Tricksters’ by Margaret Mahy is the double of Cara Delevingne!
The Pentrals starts credibly enough, with a strange first person narration of a girl watching another girl. The vantage is odd and disorienting, and it's only when you realize that the narrator is the girl's shadow that the angles lock, and you can finally orient yourself in both space and understanding. The narrator, Antares, is the shadow of Violet, a denizen of the futuristic city of Talline, which gleams from a thousand mirrored surfaces in a canyon in the desert. The Pentrals of the title refers to beings of shadows or reflections, which in the supernatural architecture of the novel, are sentient beings enacting penance for something done in another life.
As a set up, this is neat stuff: the brightness of the future city juxtaposed against the Gothic shadow, the doppelganger reading and commenting on the bright lived life through its negative image. Unfortunately, this tense imagery is squandered, and quickly. Not only does The Pentrals deny the reader much in the way of resolution, but the basic mechanics of both the supernatural world of the Pentrals and the society of Talline are so confused (or, often, downright stupid) that any resolution is close to meaningless. Altogether, this was one of the more frustrating novels I've read in a while.
Ever wonder why Jack Black seems to resemble Paul Revere, or Donald Trump looks a lot like Gen. George Patton? Doppelgangers and clones may be the next big trend in supernatural fiction.