i wanted to ask that which books are good to prepare for iit?

@ pallavi 
frst of all for JEE read the necrt throughly , as in jee 50 percent of the question are from ncert , rest choose the books which best suits you , as every author have diffrent approach to explain the concept , so, choose the one in which u are comfortable in . 
i am listing some books below u can choose with your preference . 

1- PHyiscal chem by o.p tandon 
2- organic chemi by morission and boyd. 
3- inorganic chemi by mtg publication 
MATHS BY ml khanna / objective maths by rd sharma . 

concept of physics by h c verma , ( 2 volume ) . 

problems in general physics by i.e irodov . 

just solve these books side by side with ncert , u can clear JEE easily . 
askiitian self study package are also good , u can refr to them to clear the concept . 
ALL THE BEST . 

hope it clears the query .