28 books • 2 series
Gregor and the Curse of the Warmbloods (the Underland Chronicles #3: New Edition) (The Underland Chronicles)
Gregor and the Marks of Secret (the Underland Chronicles #4: New Edition) (The Underland Chronicles)
Gregor and the Code of Claw (the Underland Chronicles #5: New Edition) (The Underland Chronicles)