Laddertop

An original science fiction tale by the bestselling author of Ender's Game and his daughter Twenty-five years ago, the alien Givers came to Earth and bestowed upon the human race the greatest technology ever seen--four giant towers known as Ladders that rise thirty-six thousand miles and culminate in space stations that power the entire planet. Then, for reasons unknown, the Givers disappeared. Due to the unique alien construction of the Laddertop space stations, only a skilled crew of children can perform the maintenance necessary to keep the stations up and running. Back on Earth, competition is fierce to enter Laddertop Academy. It is an honor few students will achieve. Best friends Robbi and Azure, two eleven-year-old girls who are candidates for the academy, will become entangled in a dangerous mystery that may help them solve the riddle of the Givers--if it doesn't destroy the Earth first.