A Course of Pure Mathematics
Hardy's book became a classic soon after it was published. It is still an excellent text for the motivated undergraduate student of mathematics.
A Mathematician's Apology (Canto Classics)
How to Solve It: A New Aspect of Mathematical Method (Princeton Science Library)
Calculus, 4th edition
An Introduction to the Theory of Numbers (Oxford Science Publications)
The Man Who Knew Infinity: A Life of the Genius Ramanujan
A Book of Abstract Algebra: Second Edition (Dover Books on Mathematics)
Book of Proof
Fourier Series (Dover Books on Mathematics)
Combined Answer Book For Calculus Third and Fourth Editions
Introduction to Graph Theory (Dover Books on Mathematics)