I have some information about important books to read and practice for 2021:
Between the best mathematics textbooks for self study at University level, i have the ten most ever needed to learn from.
The Math books You’ll ever need are:
1 - Contemporary Contemporary Abstract Algebra writer author by Joseph Gallian.
2 - Abstract Algebra by writer authors David S. Dummit and Richard M. Foote.
3 - Introduction to Algorithms, Third Edition by writer authors Thomas H. Cormen, Charles E. Leiserson and Ronald L. Rivest.
4 - The Art of Computer Programming, Volumes 1-3 Boxed Set by writer author Donald E. Knuth.
5 - The Calculus Lifesaver: All the Tools You Need to Excel at Calculus by writer author Adrian Banner.
6- Calculus Made Easy by writer author Silvanus P. Thompson. 7- Calculus, Vol. 1. by writer author Tom M. Apostol.
7 - Calculus by writer writer author Michael Spivak.
8 - Calculus, Vol. 2 by writer author Tom M. Apostol.
9- Calculus On Manifolds by writer author Michael Spivak.
10 - Mathematicians: An Outer View of the Inner World by writer author Mariana Cook
Still there are many more fro students to read in this sections:
Abstract Algebra, Algorithms, Calculus Helpers, Calculus I, Calculus II Coffee Table, Combinatorics, Differential Equations, Encyclopedias of Mathematics, Foundations of Mathematics, History of Mathematics, Information Theory, Linear Algebra and Geometry, Mathematical Methods, Numerical Analysis, Number Theory, Precalculus Probability, Real and Complex Analysis, Statistics, Topology.