My daughter did books A,B, and C and then book 1 in the Explode the Code Series. She is just finishing up K. When we finished book 1, we started on book 2, but I realized that it might be wiser to take our time and back up to book 1 1/2. I'm glad we did this book. It gave her additional reinforcement. This book adds in additional words similar to those in book 1. I like the whole series and my daughter is practicing her handwriting, learning phonics, practicing her reading comprehension, and learning how to spell all in one program. I think these books are wonderful!