The book of dead days - Marcus Sedgwick

The days between 27 December and New Year's Eve are dead days - days when spirits roam and magic shifts restlessly just beneath the surface of our everyday lives.
There is a man, Valerian, whose time is running out, who must pay the price for the pact he made with evil so many years ago. His servant is Boy, a child with no name and no past; a child he treats with contempt, but who serves his master well and finds solace in the company of his only friend, Willow. Unknown to any of them it is Boy who holds the key to their destiny.
Set in dark threatening cities and the frozen countryside in a distant time and place of the author's making, 'The Book of Dead Days' conjures a spell-binding story of sorcery and desperate magic as Valerian, Boy and Willow battle to stop time and cling to life. Beautifully evoked, dramatic and emotionally powerful, this is a real page turner.