The Beast of Babylon — Charlie Higson

Eleven Doctors, eleven months, eleven stories: a year-long celebration of Doctor Who! The most exciting names in children's fiction each create their own unique adventure about the time-travelling Time Lord.
When a girl called Ali pockets a silver orb that falls from the sky, little does she realize it's her ticket to seeing the universe! Desperate to retrieve the mysterious object, the Ninth Doctor agrees to let her join him on a dangerous trip to ancient Babylon. Together they must join forces to stop a giant Starman from destroying Earth before it's too late!
Author Charlie Higson puts his own unique spin on the Doctor's amazing adventures through time and space.