Two deadly rivals fight a battle of wits along the treacherous waterways of an alien world. In Showboat World, Jack Vance returns to the exotic and fantastic Big Planet, a world colonised by criminals and outcasts. Apollon Zamp is adept at dodging the dangers of sailing a showboat from port to perilous port along the Vissel River. And his labours aren't helped by his archrival, Garth Ashgale, constantly threatening to undermine Zamp's plans. But their…