What is the difficulty level of the JIPMER MBBS entrance exam as compared to AIPMT? Which are the best reference books for the JIPMER entrance exam?

Here are some points I gathered online regarding your question. This might give you a suggestion on how to approach and what to expect.

• JIPMER entrance exam is about having a combination of speed and accuracy. 
• There is not much difference in difficulty between the two papers i.e, NEET/AIPMT and JIPMER. They both ask questions from NCERT. 
• Questions asked in JIPMER are small and simple. It is not confusing. 
• For JIPMER exams it is recommended that you solve previous year’s questions to clear your concepts, revise formulas and revise the name reactions of organic chemistry.
• Physics, Chemistry, and Biology are quite easy as compared to other entrance exams, with NCERT you can solve 130-140/160.
• If you have prepared well for AIPMT then you won't face much difficulty in the other exams.
• English plays an important role in selection.

No new books are recommended at this time. Go through the topics from the same books and notes. You will definitely score good marks.