Intended for written exam you can take help of MKC Publication Book for NDA written exams. I think it’s more than satisfactory. Furthermore, your basic NCERT mathematics should be very strong in sequence to clear the subject cut-off of the mathematics exam. As far as the physical is worried I don’t sense there is any must to focus on that as long as you are in a good physical condition. Your centre of attention should be more on the SSB and start preparing for it as soon as the NDA written is done. a lot of aspirants wait for the call letter and then start with preparation when the time is too less. So if you are positive enough about cracking the written exam then please don’t misuse time on waiting till the written result or call letter. For the preparation of SSB, you can visit a range of websites like Major Kalshi Classes Pvt. Ltd. which will provide you with a complete insight into the whole process. All the Best!