Online Courses v/s Books

Hi login4imtiaz
I have also the same condition with you.
But, you can watch previous post from this site.
In fact, there are many similar question on former post.
In sum, I believe you could obtain satisfied answer from this site.

In my experience, I have brought a series of kaplan's and princeton's workbook to prepare my GMAT. However, I find that to studying princeton's materials is easily digest and recognize because their questions is more easy than that of actual test. Thus, based on princeton's stuff, I began to study Kaplan's book and then do its quiz or practice question even though I still can not do well on this exercise.
To tell the truth, I think kaplan's stuff is great and sufficiency practice for crackinging GMAT test because some of its questions are rather tough.
This practice is great opportunity to drill skills and strategies.
In addition, official guide is more important than any other prep books.
I still think official guide is necessary because it contains past-actual questions which are simliar to questions you encounter on actual test.

As for math, you could do some math review workbook to refresh your math concept. I think kaplan's math book is a wise choice.

I don't know understand which one is more great betwwn on-line and book. Therefore, I could not give you any opinion.

Above it is my personal experience and opinion.