Which book you would suggest for preparation for CAT?

For enhancing you Vocab Power go for Word Power Made Easy by Norman Lewis It is brilliant book that helps you build a strong vocab. I would suggest you to buy this book and keep reading it again. The book does not forces you to memorize any word, it explains the origin and history behind the word

You can refer to quantitative books like Arun Sharma, Wren & Martin for Grammar, and practice DI, LR questions from question banks available over internet. Scoring high percentile is just not about giving time to preparation. Its also about managing your time and making correct choices in the exam.