Fantasy book with an adopted son called Boy

Question

Around about 2010 I read a fantasy book in which the main character was an adopted son called Boy. The adoptive father was a stage magician, but it seemed to imply that there might be some real magic behind at least one of his tricks (he could disappear by saying something like 'away with the fairies'). I recall it seemed to be set in a late Victorian era, possibly in London. The father lived in a tower overlooking the city, and had a powerful (perhaps magical?) telescope. There was an emperor / king who ruled the land and might have been an enemy of the father, and it was implied at various points that the boy might actually by the offspring of the emperor and next in line to the throne.

• A fairly well known Male British author I think.
• Published around 2010, first book in a series.

Answer 1

The Book of Dead Days by Marcus Sedgwick

THE DAYS BETWEEN Christmas and New Year’s Eve are dead days, when spirits roam and magic shifts restlessly just beneath the surface of our lives. A magician called Valerian must save his own life within those few days or pay the price for the pact he made with evil so many years ago. But alchemy and sorcery are no match against the demonic power pursuing him. Helping him is his servant, Boy, a child with no name and no past. The quick-witted orphan girl, Willow, is with them as they dig in death fields at midnight, and as they are swept into the sprawling blackness of a subterranean city on a journey from which there is no escape.

Search terms of fantasy book "stage magician" boy "named boy"