Children of the Comet — Donald Moffitt

In Donald Moffitt's brilliant cosmic adventure, Torris, son of the Facemaker, knows only his small community at the base of the great Tree on a comet with almost no gravity or atmosphere. Torris's daily struggle for survival includes harvesting frozen air to keep breathing, dodging flutterbeasts, and hunting meatbeasts for food.
 
When the time comes to make his vision quest to the top of the Tree, Torris is completely unprepared for what he finds: a thieving and hostile fellow quester; Ning, a female hunter in search of food to save her family on a neighboring comet; and humans from a massive starship that has spent billions of years crossing the galaxy from Earth's solar system.

Perfect for fans of Arthur C. Clarke, Larry Niven, and Peter F. Hamilton, CHILDREN OF THE COMET is an enthralling space odyssey about a young man grappling with unexpected cultural differences and learning to adapt in the face of an uncertain and rapidly changing fantastical future.