H.W.
B.,
I have this book and chose not to use it. It expects children to learn symbols they are unfamiliar with, not just letters, and honestly, when I looked over the lessons, they seemed very dry, teaching reading without the richness or context that teaching whole language often includes.
Please, consider letting it go. I promise you, the kindergarten teacher KNOWS how to do this with groups. They really do not expect kids to know how to read when they walk in. Some will, some won't, and most will leave kindergarten reading at their grade level.
Let him enjoy you at home as mom, continue to read and play games with him. I'm not saying you should not teach him, but this method is usually reserved for children who were struggling with reading after receiving classroom instruction. (and I have that from a special ed teacher.)
ETA: My little sister will tell you that I "taught" her to read.. I read to her all the time when I was 8 and she was 6. Lots of the Dr. Seuss Beginner books, over and over and over. Memorizing the rhymes, the words, slowly putting it together herself. It was fun.