Hello, 

According to your question you have given NEET UG two times and you can give the exam one more time. The best book to refer for NEET as such is not available. There is a wide variety of books like the NCERT books for class 11 and 12 which are usually enough for preparation. You can refer other books for reference. Visit the following link for more details

https://www.google.com/amp/s/medicine.careers360.com/articles/best-books-for-neet/amp

Good Luck.