Hiii

For preparing biology for NEET exam you must simply focus on NCERT book and by heart each and every bit of the book. The complete paper is set from the NCERT itself. Once you are done with the NCERT you can take up any reference book to practice the questions to improve your performance.
For AIIMS you will require some other books along with NCERT as 10% questions are out of NCERT .
Here is a link you can use to know about the best books.
https://medicine.careers360.com/articles/best-books-for-neet
https://medicine.careers360.com/articles/best-books-for-aiims-mbbs

Thanks!

Hello Vidya,

It depends upon you. You can read online also without coaching with self study.

In order to score a good marks in the NEET 2019 examination, you should read NCERT books of Physics, Chemistry & Biology of class 11th & 12th at least 2 or 3 times for basics, your basics should be very clear upto class 12th. After that HC Verma for Physics (part -1&2), Biology by Trueman (volume-1&2) and Pradeep Guide on Biology, OP Tendon for Physical & Inorganic Chemistry, and Organic Chemistry of "Arihant Publication" for detail or extra knowledge. Your study materials provided in the coaching could also be helpful. You can also read more books whose names are given in the link given below
Https://medicine.careers360.com/articles/best-books-for-neet
You should also try to solve the previous years question papers, this helps too much and you should also give the mock test to rectify yourself and build your confidence level.
To know more about preparation tips, syllabus, important topics, prevoius year questions with the solution, chapter wise weightage & the best books, you may visit the link given below
Https://medicine.careers360.com/articles/neet-2019
https://medicine.careers360.com/articles/neet-chapter-wise-weightage-and-important-topics
In this way you will be able to prepare yourself well and score a good marks in the NEET exam. 
Thanks for query on this platform, you may visit again
All the best.