Northern Lights by Philip Pullman

The first of the "His Dark Materials" trilogy, Nortern Lights is set in an alternative England and Northern Scandinavia. A very good adventure story for childern; very scary baddies, very clever and strong goodies, armoured bears, witches, sea voyages, balloon flights. Unfortunately this story perpetuates the myths of the noble barbarian (the armoured polar bears are 'better' in their 'natural' state), and of the honest gypsy (boat-dwelling people of no fixed abode are honest and honourable, despite living outside the reach of the law.) The unsatisfying ending is unavoidable, I suppose, it being the first volume in the trilogy.