Does writing a book improve your chance for getting scholarship for applying PhD abroad? As you know there are many candidates competing for winning the scholarship for their PhD program, specially the ones who are applying abroad. So, having better skills likely spell to overcome the other candidates.
I have two SCI papers in my field. So I don't have a very bad research background as a graduated student of electrical Engineering for M.SC. degree. But, recently, I've started to write a book in English. The content of book is very general and simple but still can be fitted in my field. The book title is going to be 'Technical use of English language in electrical engineering'. This book is one of the courses of Electrical Engineering for undergraduate program in our countries.  

So, since the books are not usually peer-reviewed, I was wonder to ask:  


How much does writing  a general and simple book in your field help
you to get a good scholarship for PhD program?
Is the effect of writing a book more than a namely SCI research paper?
Is the affects of having a book variy in different countries? If
yes, please tell me about Australia, US and Canada for precise.
Is it okay if I self-publish the book or I need a good publisher?
does it compensate my bad GPA by any chance?
finally, what are the advantages of having a book as a graduated
master student?
The goal of a PhD is to teach you how to do research. Teaching is not the primary goal of the PhD. Book publishing is also considered something that can be detrimental early on in one's career, since it takes time away from the other more important goals (advising students and postdocs, peer-reviewed publications, grants, teaching, committee work, etc.).

That said, a well-written published book probably can't hurt your chances. If, however, it's riddled with poor writing and technical errors, it will not help and may even do some harm.