HI,

The reference books for the NPAT exam are as follows: -

Chand Quantitative aptitude for Quantitative examinations by R.S.Aggarwal

S.Chand Modern Approach to logical reasoning by R.S.Aggarwal

Ramesh Logical and Analytical - A.K Gupta

IPMAT:

Crack the IIM Indore IPM Entrance Exam’, published by Pearson 

If you want separate books for preparation of separate sections you can go for-

Class XI and XII Mathematics by R.D. Sharma

Quantitative Aptitude for Competitive Exams by R.S. Aggarwal

Word Power Made Easy by Norman Lewis

Better English by Norman Lewis

English Grammar and Composition by Wren and Martin

You can use the link below for downloadng sample papers.

Https://bschool.careers360.com/download/ipmat-sample-papers-previous-years

Best of luck!