In Great Waters, By Kit Whitfield Jonathan Cape,

The secret in fiction of showing how things remain humanly the same, no matter how bizarre, is to establish your ground rules from the start. Kit Whitfield's second novel starts by throwing us in at the deep end. Her young half-merman, Henry, is reared among those who are, and are not, his kind: he has legs where they have single, muscular tails. In due course, his mother grows tired of helping him to his food and abandons him on the shore. He becomes a pawn in the politics of a court that has as much resemblance to the Renaissance courts of our history as his people do to hunter-gatherers who do not live in the depths of the sea – not all that much, and more than you might think.

Henry is taught landsmen's weapons and history, and generally trained up to be a royal pretender. Meanwhile Anne, the younger of two princesses, observes quietly, and decides what alliances she will make. Anne, like other royals, has the folk of the sea in her bloodline, a bloodline hopelessly weakened by inbreeding. Then her mother is horribly murdered in her bath, her grandfather, the king, becomes frail, and Anne has decisions to make.

This is a powerfully intelligent novel about two young people trying to survive the plots of their elders and the cards dealt them by circumstance. Whitfield's strength, here as in her werewolf-noir first novel, Bareback, is a bleak refusal of sentimentality. People cannot allow themselves the luxury of justice or revenge.

There are false notes here: the back story, in which a near-legendary saviour unites the people of Venice with their merman neighbours, has more incoherencies than it needs. And the political dispensations of this world are too like our own, even after seven centuries of intervention from the sea. On the other hand, Whitfield is good on the tawdry luxuries of medieval courts and the savage sublimity of life beneath the sea. The supreme merit of this chilly book is its refusal of consoling prettiness.