To have read this book, I could understand the vocabulary and grammar it up because this book is described on the reverse side, and this book can practice reading simple vocabulary.
To read this book, I can understand the vocabulary and grammar you up. Because this book is to explain the background. And the book can be read as an intern. With simple vocabulary
To read this book, I can understand how the vocabulary and the grammar. Because this book is explained in the back. And this book can be read again with the training vocabulary easily.