This is the second book in a series; its predecessor, Flood, which I haven't read, saw the near-future Earth threatened by catastrophically rising sea levels, and Ark follows the story of a group of young survivors sent to colonise a distant planet in order to continue the human race. I will look out for Flood but didn't especially feel the lack of having read it hampering my enjoyment (it is fairly easy to spot which characters must have been in the previous book). I did, however, feel that Ark is weakened as a novel by the number of loose ends left unresolved, in particular the characters and groups of characters who drop out of the narrative, fate unknown, some of whom will presumably to be brought back again (or definitively killed off) in future volumes. And in general, while Baxter's writing always at least teeters on the brink of greatness, this doesn't quite make it. The basic idea is a great sensawunda concept - the broad brush strokes of the mechanics of building the Ark, and the human factors which screw up its makers' plans, are depicted in full glory. But at a human level Baxter's characters don't always sound like, say, 22-year-old women thrust into leadership positions; and they sometimes make peculiar choices which enable him to extend the narrative in the direction he wants. The book becomes more episodic towards the end, and I felt Baxter was rather rushing to finish it. So I wasn't completely satisfied, and this will rank below Yellow Blue Tibia on my BSFA ballot.