As the description says, it's a supplementary reader and it helps a lot. I've just begun my XI studies and I'm not paying attention to my last optional subject Economics just now (Maths...) but yet reading this book I bought for future purpose gave me an idea about the contents of the main textbook.
If you, as the introduction (or IDK if it was preface) says, read it thoroughly and complete all the task given, you're surely going to get WAY better: the TARGET advantage. It's like not simply ...