These books are what i would consider the best books for self-study. (I have gone through many textbooks after i went back to school to study statistics.)

• Real Analysis: A Long-Form Mathematics Textbook

• Proofs: A Long-Form Mathematics Textbook

• Mathematical Logic Through Python

• A Course in Calculus and Real Analysis

• A Course in Multivariable Calculus and Analysis

• Differential Equations With Applications and Historical Notes

• Probability and Random Processes (Grimmet)

• Probability Through Problems

• Fifty Challenging Problems in Probability with Solutions

• The Simple and Infinite Joy of Mathematical Statistics

• An Introduction to Error Analysis