This 4 Books Set Contains: Explode the Code, Book 1 (2nd Edition) Explode the Code, Book 2 (2nd Edition) Explode the Code, Book 3 (2nd Edition) Explode the Code, Book 4 (2nd Edition) Explode the Code.This 4 Books Set Contains: Explode the Code, Book 1 (2nd Edition) Explode the Code, Book 2 (2nd Edition) Explode the Code, Book 3 (2nd Edition) Explode the Code, Book 4 (2nd Edition) Explode the Code.