He is famous for his tetralogy The Age of Unreason, a steampunk/alchemical story featuring Benjamin Franklin and Isaac Newton.

In 2003 he began a fantasy series titled The Kingdoms of Thorn and Bone, the first volume of which was The Briar King.

In 2009 it was announced that Keyes would be writing two novels based on the successful computer game The Elder Scrolls IV: Oblivion.

[4] Greg Keyes builds his stories around multiple main characters who meet only rarely, but allow the reader to follow different threads of the same events.

For example, Stephen Darige, one of the main characters in The Kingdoms of Thorn and Bone, is an adept linguist, and his knowledge and skills play an important role in the development of the story.