The Underland Chronicles

1. 

   Book 1

   Gregor the Overlander

   Suzanne Collins

2. 

   Book 2

   Gregor and the Prophecy of Bane

   Suzanne Collins

3. 

   Book 3

   Gregor and the Curse of the Warmbloods

   Suzanne Collins

4. 

   Book 4

   Gregor and the Marks of Secret

   Suzanne Collins

5. 

   Book 5

   Gregor and the Code of Claw

   Suzanne Collins

6. 

   Gregor

   Suzanne Collins

Book data and covers from Open Library (openlibrary.org).