I want to prepare only for jee mains so that I can secure a rank between 15k-20k and get admitted to a good nit

For JEE main, yep NCERT will be really useful. Other than that, try:

1. HC Verma for physics

2. RD Sharma for maths

3. P Bahadur for physical chemistry

4. NCERT will do for organic and inorganic chemistry (along with some coaching modules if you can get them somehow)

5. This is really important: DO NOT FORGET TO DO PREVIOUS YEAR PAPERS AND SOME SAMPLE PAPERS BASED ON CURRENT FORMAT AND SYLLABUS. It helps a lot. Really.

it will be a really daunting task to finish off your preparation in 5 months alone because if you haven't had the motivation to start preparing till now, then it is going to be so tough, trust me.

Now lets plan your schedule so that you can finish all of the above in time (if you can finish all of the above books easily and master them, and also get a 90%+ score in board exams, then you, my friend are a stud. If DTU or BITS is your dream college (assuming you are from Delhi), then nothing will be able to stop you from getting an admission there).

Try finishing up NCERT, HC Verma, RD, and P Bahadur in just 3 months and no more than that. Then solve all of the sample papers and set aside the last month for revision. Do this and I don't see how you won't be able to score big. Also there is this story of an IITian who was in a situation like you before and how he cleared up IIT with intense focus and determination without being a genius (you may have read it online already but still..). I will paste it here for you.

"Those who are thinking that it's impossible to crack JEE in 5 months here is a short, true story about a boy who was able to crack JEE by preparing sincerely for 3 months itself.

There was a boy named Anirudh who woke up on a day when IITJEE forms were out. It was November.Anirudh was regretting about the time he wasted. He was not at all prepared for JEE.Not even the basics.

But the positive thing about Anirudh was that he never gave up and said to himself that "there is no gain without pain". I will crack JEE in 4 months of preparations.

You won't believe guys he kept his mind on cracking JEE in 3 and a half month and worked sincerely for the exam. He studied 10 to 12 hours daily and increased it to 12 to 13 hours after January.

He even studied board exam portion too since he had to answer his boards in the same year.

Anirudh was very weak in physics and had forgotten 11th mechanics and chemistry organic. He was proficient in maths only till board level.

But inspite of all these hurdles he kept his cool and started the preparations all over again right from the beginning.

So how he started….

Physics

He read NCERT book of physics as fast as possible and completed it in 1 week

Then he solved each and every problem in HC Verma….and if he had any difficulty he solved them soon.

He read Resnick Halliday thoroughly and even solved problems from it.

In chemistry

Started with NCERT and followed the same method as in physics.

Read Morrison Boyd and solved relevant problems.

And maths

He took up coaching material and studied it religiously.

You won't believe guys Anirudh mastered his concepts till end of March and scored decent percentage in boards and cleared IITJEE with AIR-1278.

Today he is studying BTech in Aerospace Engineering from IIT Bombay.

If Anirudh can do it then why not you….

Anirudh isn't any gifted student but is same like everyone of us.He is just an average student.

But he also swore that he wont be postponing any more things in his life .

So what's the conclusion

Studying sincerely for 3 to 5 months = Studying not so seriously for 2 years

There is a lot of time for JEE and start for it now itself if you haven't started yet.

'Whenever u need to learn something start with what is necessary, then do what is possible & doing that u would suddenly realize that u r doing the impossible'

Don't worry, JEE is not an unachievable task it's just that you think it's unachievable. Leave no stone unturned.

Nothing is impossible since Impossible also says I M Possible"

source: Cleared IIT-JEE in 3 months!!!

ps: if he can clear IIT in such a short time, then you should easily score big in mains

goodluck..!