How do I score well in 11th std CBSE? Should I prepare for JEE? which book do you prefer?

There are no such relevance of scoring good in CBSE 11th compared to the preparation of JEE. If you are aspiring to study engineering from IIT's or NIT's then you must prepare for JEE as this institutes are the best.

Now to score good in CBSE 11th you need to be very sincere with your studies. Every year students gets frustrated with the 11th in two subjects mainly in Physics and Chemistry. So don't get frustrated. Its very real for you that Physics can feel tough in 11th because there is a good shift in the technique of solving problems we are used to till 11th. So you have to persevere and to be sincere with your studies. For physics, study the derivations well and try to practice the derivation twice. If you follow this then you will get a generalized view of the concept and its applicability in different physical conditions. Now for chemistry its more about memorizing reactions and stuffs. Although in physical chemistry you can do it by remembering formulae. Thus if you don't like chemistry, Physical chemistry is the part you will be fond of. For Inorganic reactions try to understand the mechanisms as much as possible. This will help you to get used to with the subject. And the most important thing is that Physics, Chemistry, Mathematics all this subject needs a lot of practice. So if you practice well and study the subject by understanding the subject then you will do great in CBSE 11th.

For JEE and CBSE you may follow the same books such  as NCERT for all three subjects, DC Pandey/BM Sharma Physics books set, HC Verma volume 1 and 2. For chemistry Physical Chemistry you can go for P.Bahadur (problem solving), RC Mukherjee, Organic Chemistry OP Tandon etc.

To know about the book list which will be helpful for your JEE MAINS visit the link below:

https://engineering.careers360.com/articles/best-books-for-jee-main

I hope this answer helps. All the very best for your future endeavors!