Epistle to the Colossians
This book has been long thought to have been written by the Apostle Paul to the Christians in Colossae, a small Phrygian city in modern day Turkey. Some modern scholars think it was written by a follower of Paul based on how it describes Jesus.  They believe those ideas took some time to be thought out. It is not as certain that Paul wrote this letter as it is with his other letters.