What are all the books referred for GPAT EXAM? Best author for each subject....and what type of preparation should be done before the exams?

There are numerous books in the market but experts and top educators recommend these books- The Pearson Guide to GPAT and Other Entrance Examination in Pharmacy, GPAT : A Companion by Nazma Inamdar, Synopsis for GPAT by Dhawan Book Publication etc.
First go through entire syllabus and then make a proper and programmatic study schedule. You can also make short notes because making notes help you understand the topic better and during revision it helps a lot. Write down all tbe formulae, charts, diagrams in one notebook so that you can checkbit whenever needed. Once you complete your syllabus, you must solve previous few years' examination papers and sample papers. Give mock tests as many as possible.
And at least 15 days before the exam, you should start your revision. Don't look for more weightage or less weightage, just revise from first to last. Don't for for something new during last days. The more you'll practice the more you'll get to score good. Go through this- http://pharmacy.careers360.com/articles/best-books-for-gpat