Test preparation

Some of the newest & demanding specialisation include:
International Business
The 21st century global marketplace mandates professionals with an international perspective. The MBA in international business offers students an understanding of international operations. Grads who have concentrated in this field are well-prepared for careers with multinational corporations. Leadership
This quickly growing concentration offers an interdisciplinary education focused on critical aspects of contemporary business success, including finance and marketing, as well as beneficial business practices, such as conflict resolution, team building and corporate communication. R
Strategy
Another rising field, this specialisation prepares students for careers managing complex market dynamics. Coursework includes analysis across a variety of factors, organizational structure, and market evolution and others. Entrepreneurship
A concentration in entrepreneurship not only prepares grads for careers as successful entrepreneurs, but also for managerial positions within companies which prioritize innovation, along with the leaders that go along with it. Read more about the MBA in Entrepreneurship here. Innovation
A concentration in innovation offers students a foundation comprising the essential skills, knowledge and critical thinking which promote effective innovation and innovation management.

There are multiple books available and they all are good. You can start with for quantitative ability:
1. Arun Sharma published by Tata McGraw Hill.
2. The Arun Sharma Complete CAT Digest by Tata McGraw Hill.
3. Quantitative Aptitude for Competitive Examinations by Abhijit Guha.
4. Quantitative Aptitude for CAT and other MBA Exams by Trishna Knowledge Systems(Pearson) has many practice exercises in increasing difficulty for a gradual transition.
For verbal reasoning and reading comprehension:
1. How to prepare for Verbal Ability and Reading Comprehension by Arun Sharma and Meenakshi Upadhyay (Tata McGraw Hill).
2. Word Power Made easy by Norman Lewis.
3. Barrons Pocket guide to vocabulary.
For Data Interpretation and Logical Reasoning:
1. Book by Arun Sharma (Tata McGraw-Hill ) where you will learn the concepts.
2. Trishna's Verbal Ability and Logical Reasoning by Pearson.
All these books are of great help and have come across various internet materials as well, take mock test and practice questions from various types of entrance test.
Best of luck!