Order of Petaybee Books
The Petaybee series consists of two young adult sci-fi trilogies by novelists Anne McCaffrey and Elizabeth Ann Scarborough. The series is focused on a major who goes by the name Yana. Yana is a disabled soldier who is sent to a glacial planet called Petaybee to spy, but it turns out that the planet is actually beginning to become sentient. Yana must now protect Petaybee from corporations attempting to exploit it.
The Powers trilogy began with Powers That Be in 1993 and ended with Power Play in 1995. The Twins of Petaybee trilogy began in 2005 with Changelings and ended in 2008 with Deluge. Below is a list of both Petaybee trilogies in order of when they were originally released: