Greetings,
There is no such book known as the best book for preparing for NEET UG. There are a number of books available in the market. The choice varies from person to person.
However for multiple choice questions you may refer to the Dinesh Physics, Chemistry and Biology books. They provide a wide variety of multiple choice questions for your practice as well as previous years papers.
For quick revision of the respective subjects you may refer to MTG Physics, Chemistry and Biology. They provide concise information and points to be remembered for the examination.
It is advisory to give a thorough revision through the NCERT books of Physics, Chemistry and Biology. A vast number of questions are based on the text given in NCERT books.
It is also advisory to avoid opening any new books right before the days of the exam. Revision from books that you already read is advised.
Do not worry about the tough topics that you face difficulty in covering. Focus on the topics already covered. Cover as much of the syllabus as possible and revise as much as possible.
I hope this piece of information proves to be useful to you.
Please feel free to refer back here in case you have any further queries.
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Wish you all the best in all your future endeavours.
Good luck.

It's always the best option to study your coaching notes of your teacher classes and then the college packages