Skies of Pern by Anne McCaffrey

Anne McCaffrey's Pern series has been running successfully for so long that most of the Dragonriders' original problems have been solved. In The Skies of Pern, she confronts her standard cast of characters with the consequences of those solutions, consequences that are a whole new set of problems. Now that the Red Star has been pushed to another orbit, there will only be a few more ravenous Threads descending from it for them and their dragons to fight--and what role will that leave for them?