Hello Aspirant,

You didn't mentioned for which class you have asked this question. So I explain you for both 6th and 9th standard.

Best publishing books and guide for Sainik school is of Arihant publication. This publication having best reviews.
With solving the book you also have to clear your basic concepts according to the syllabus. Practice more and more mock tests, it will boost your score, confidence and preparation.

Hope this will help you.

Thank you!