There's no single book titled "Best Seller CBSE Class 9." CBSE (Central Board of Secondary Education) doesn't publish a single "best-seller" textbook. CBSE uses different textbooks for different subjects, and various publishers offer books aligned with the CBSE curriculum.
To get a summary, you need to specify which subject and which textbook you're referring to. For example, you might ask for a summary of the *NCERT History textbook for Class 9* or a summary of a specific chapter within a particular publisher's math textbook.