After reading this book, buy a copy of Nan's Miscellanies of the Book of Changes. Although this book is not so easy to understand (but not obscure), it is not deep to study. I recommend this book, because it is written dialectically, and it won't make you fall into superstitious misunderstanding as a beginner. After reading this book, it's up to you to understand. Are there any other books? Take a look at it when you are free.