Take a look at this.
Further facts later.

Substandard books identification.

How do you identify useful book and discard substandard book?

Is the book in the English language?   

Is the book relevant to school, college, or university education?   
Is the book in question-and-answer format in the English language?  
Can the book enhance any one of these: abilities/skills, professions, products, subjects, services?  

If yes to all above questions relevant to a book the book is useful.  

These are basic questions relevant to evaluating quality of a book.
There are many more.   
A book may be in the English language but not in question-and-answer format; that makes another book with question-and-answer format better.