My son just turned three in August, but he has already completed this book. We did a few pages everyday - I think we spent a couple of months on it. He is now able to write upper and lowercase letters, and can do simple math concepts, such as greater vs. lesser, which group has more...there are mazes, coloring activities, and a variety of lessons to teach shapes, sizes, counting, writing, etc.
What I liked best about this book is the different phrases that they use in the instructions. My son learned the relationship between phrases "which ones match" and "where does it belong", "which one is different" and "which one is not the same"...just to name a couple. My son immediately applied what he learned from the book to his everyday activities, so I know that he did absorb some, if not all, the lessons.
Since this book is a combination of smaller books from School Zone, it's not necessary to buy the others unless your child has trouble with a particular area. My son struggled with the pages dealing with "beginning sounds," so I bought him the book that is just activities to teach beginning sounds.
I prefer School Zone to all other preschool workbook series, with the exception of Kumon.