Organic chemistry by Joseph Hornback is the only book that is written to master the concepts like a pro with so easy to understand language for students. This book has chapters based on mechanisms that a reaction follows unlike dividing chapters by functional group.
This is very much an advantage as students preparing for IIT Advanced prepares mechanism for reactions for every chemical reaction. So preparing the same old mechanism wise makes reactions easy to understand and apply in exams.
So I strongly suggest to follow up this book if your goal it for IIT.