Hi Manish,

yes of course you can study from NCERT books for NDA as the language used to explain the concepts in these books are very easy and comprehendable.

one more thing once you have completed your prepaprtion from ncert books always opt for other books as well to practice espaecially for exams like maths.

you can also lookout for ICSE books as do have a lot of practice model papers and solved questions that will further help you in getting thorough with your subjects.

The mathematics and english play a major role in your clearing the written examination. If you have command over , 11th and 12th  mathematics , and reasonably good english , then half of your task is sorted.

After that , you may go through the previous years papers and that will suffice. Remember, clearing NDA is not a big deal, to clear SSB is a real challenge. But your written marks count in final merit list and may help you in getting the arm of your choice in NDA.

Best of luck.