Hey,
The primary book for Organic Chemistry is NCERT.
You must get equiped with the concepts of NCERT Organic Chemistry.
You can refer to other books that will give you in-depth explanation of the concepts of Organic Chemistry that you refer to while preparing for any competitive examination like Medical or Engineering entrance examinations such as:
"A Guide Book to Mechanism in Organic Chemistry" by Peter Skyes
"Organic Chemistry" by Clayden
"Organic Chemistry"by  David R Klein
Name Reactions by Jie Jack Li
Hope this helps.
Good luck.