Sorry friend, but you should enhance your attitude for general studies. Paying equal attention to every subject is crucial for exam strategy. The range and depth of asked question is very intense. For Science, You can start with NCERT books of XIth, XIIth. If still you need to clarify the basics, Xth standard books can help you. After this you would need to keep the updates and important events in the field of Science, current and of late as well. Science segment of papers, like The Hindu and magazines like Pratiyogita Darpan will help you in particular and in general as well. Still you can look for Upkar’s guide for General Science and Unique Guide for Science.

Don’t you think that many of the good books are available in English? Any suggestion for the same subject in Hindi?

Well, there are good books in Hindi also. First of all if you have your basics clear, then you have done the 70% already. NCERT books in Hindi are there for you. Then the Upkar publication has books in Hindi for general studies and Science subjects.