Hello,

Book gives information about something. it can be or may not be helpful to crack the exam. It is advised to follow the prescribed book for entrance preparation. if you are not feeling helpful then solve previous year papers and see if there is any question asked directly or indirectly from the book.  You can also prefer reference books for more assistance for preparation.

Sometimes they ask questions directly from the book but it is not necessary they will do every time. So to crack a exam it is important to understand what you are reading. if you understand then you can remember.

Content can be lengthy but you have to prioritize as per your strength and read in such a way that it will be helpful for you.

Hope it helps!