English Grammar in Use. I recommend it to all my students.

Hi, I use Oxford Practicing Grammer, it's good for learning and practicing English

would like to improve my englsih knowledge if u can come on skype for practice VENKAT.SCT this my id

http://www.perfect-english-grammar.com/index.html is a very useful one 

Those are good books.But just learning grammar rules and doing exercises is not enough.You need to use the language in context,read,write,talk and so on.Otherwise the rules will not stay in your head.