Is there any good book for general organic chemistry which provides a good concepts about isomerism and important rules

I think you should buy organic in my pocket by er. Dushyant kumar. His video lectures will make your concepts crystal clear with a lot of solved and unsolved examples.

dear anushka 
ya , you can try out the handbook in chemistry by arihant , thats good for both shortcut and problem solving tricks . 
and also , if u want full detail stepwise explanation of reaction mechanism , u can try out perason publication organic chemistry book . 
and donot forget to try out askiitians study material also . 

ALL THE BEST 
REGARDS