Hello Debasish,

Indian Institute of Technology(IITs) take admission to undergraduate courses through a 2 phase selection process, JEE Mains and JEE Advanced. One has to necessarily give these exams and then attend the JOSAA counselling to get admission. For admissions to M.Sc. courses, the IITs conduct the IIT JAM exam and conduct a counselling on the basis of its merit list.

While most students start preparing for JEE exams from class 11th, but starting early is always a good option. As for your question, the best books in my opinion would be the BMA foundation books. They are the best for building good a good foundation for JEE exams. You could also join an institute like FIITJEE, they start admitting students from class 6th.