A class set of ocarinas and a CD-Rom work perfectly well by themselves. Books are useful if you want to send children off to practice individually, in small groups, or at home. Books are also very portable for carrying in to assembly, or to other venues where you may like to perform without having to take technology with you. Playing from Book 1 is also an important skill to learn, as reading familiar music from this book will prepare a class to progress on to other music books. So whilst the CD-Rom is meant to work without books, keep a class set of Book 1 handy for special occasions, and to add variety to your lessons.