We got the Upper Case Letters book first and the kids really seemed to enjoy going the work. They really love doing this book. It's more like play then school work for them. Our "I can't do it" 4 year old doesn't want to put it away! The progressive hardness of the mazes is so gradual the kids don't have trouble transitioning through it. The patterns, colors and characters are VERY kid friendly and easy on the eyes. The whole Kumon system really has me impressed!