Hello Purayan,

You may buy any book available, but the main thing is you should follow the book, i.e. both the theory and problems part. For Chemistry, I must say, you should first prepare from NCERT. NCERT textbook for JEE Mains Chemistry is very good as it gives you deep conceptual knowledge. The Inorganic Chemistry part for JEE Mains is best recommended from NCERT textbook only. You should properly follow your class notes, NCERT Textbook and any book of a good publication company which you wish to follow. This would be enough for JEE Mains Chemistry. Hope this answer helps.
All the best!