Amit M Agarwal's Integral Calculus Book by Arihant Publications is one of the best books for Jee Main Mathematics Preparation. This book has quality problems as per the level of Jee Main, so solving these problems can help you to understand the type of questions actually asked in Jee Main. It is a highly recommended book to develop a strong basic in Integral Calculus. Integral Calculus carries enough weightage, so to perform best you must practice and prepare well. This book has variety of numerical problems to solve. But first you must start with NCERT Textbooks as NCERTs are written in simple Language which is understandable by everyone. For in depth knowledge in theory, you should prepare from NCERTs first. Then you can move on to solving complex problems from standard reference books.