what books should i refer which will help me crack the iit jee? i mean in maths physics and chemistryand pls tell me in detail including the most important topics in these subjects??

In Physics be strong in thermodynamics,optics,modern physics,electronics and communication and properties of matter.

In maths the following chapters consist of more questions 
coordinate geometry, integral Calculus , vector , dimensional geometry and determinants, trigonometry.

In chemistry get strong in Organic and Inorganic Chemistry,Physical chemistry.

NCERT and study material provided by Askiitians can help you a lot