Reeve seems to want to tell kids not to trust people; all the important adults in this story are deceitful or irresponsible, though not necessarily without some redeeming qualities. The children have to look out for themselves, which is as it should be in a children's book, of course.

Parts of the book are well written - particularly during the ascent of the mountain - but there are fleeting passages that inflict disorienting head-hopping on the reader. The view-points of all three main protagonists in less than a page is a violation of a fairly basic rule of novel writing...

It feels like Reeve can never get it absolutely right unless he's working in his Mortal Engines world.