Hello Rahul,

In order to prepare for OIR test for NDA SSB, you should read newspapers, magazines and books, practise NDA mock test and NDA question papers to be familiar with exam pattern. Make notes for harder topics to revise for the exam. List of some Best preparations Books for NDA exams are given below:

• Pathfinder for NDA & NA National Defence Academy Naval Academy Entrance Examination by Arihant
• Let's Crack NDA Exam - National Defence Academy & Naval Academy Examination by SSBCrack
• Study Package for NDA/NA Entrance Exam by Tata McGraw-Hill Education India
• Chapterwise-Sectionwise Solved Papers NDA & NA Arihant

Best of Luck!!!

Hii

You can refer to the following link to know about the best prepaaration books for NDA exams.
https://competition.careers360.com/articles/best-books-prepare-for-nda
You must work hard and keep practicing to qualify your exam.
Stay confident and focused. 
All the Best

Thanks!