Some fundamental books of Statistics are given below:
Fundamentals-of-Mathematical-Statistics_Gupta-Kapoor.pdf
2015.137863.Fundamentals-Of-Statistics-Vol-1.pdf
2015.462524.Fundamentals-Of-Statistics-Vol-2.pdf
Research Methodology Methods and Techniques by C.R. Kothari (z-lib.org).pdfSome important question-answers books:
Schaums Outline of Statistics (Murray R. Spiegel, Larry J. Stephens) (z-lib.org) (1).pdf
Schaums Outline of Probability and Statistics 897 Solved Problems + 20 Videos (John J. Schiller, R. Alu Srinivasan etc.) (z-lib.org).pdfRemaining books of various part of Statistics are also available on subpages of this page.