It actually depends upon the management exam you are appearing for because exams like CAT have stopped asking vocabulary-based questions while there are certain exams which still ask such questions.
Nevertheless, you need not refer to a  lot of books for that purpose.
What you can do as a best practice is purchase a good RC book, because this happens to be the most important section of any MBA exam. Books like
*'How to prepare for Verbal Ability and reading comprehension by Arun Sharma and Meenakshi Upadhyay',
*'' Verbal Ability and reading comprehension for the CAT' by Nishit K Sinha
*Latest RC passages and practice questions provided by study centres like TIME, CL, etc.
*and above all the best way to improve your vocabulary and reading fluency is reading newspapers, magazines, short articles, blogs, etc.

The more you inculcate reading habit, the better it is for you not just for an exam like this but for your future too because reading is the best way to gain knowledge.
Moreover every article will present some or the other new words in front of you that will add to your vocabulary.
Remember, a book with vocabulary that people refer while preparing for exams like GRE, will teach you words temporarily because ultimately your memory can stuff only those things that are used daily, in practical life, however words that you come across while reading articles will actually give you the entire context of the usage of the word, that might retain longer and linger in your memory too.
So, purchase one or two most suitable books and practice hard.
Wish you all the luck!!