The following books have been recommended by several readers. The number of recommendations is in brackets.
Lang, Serge. Algebra. 2nd ed. Addison-Wesley Pub. Co., 1984. [2]
Halmos, Linear Algebra. [1]
Birkhoff, McLane, Algebra
van der Waerden. Algebra
Atiyah & MacDonald. Introduction to Commutative Algebra
Ahlfors, Lars Valerian. Complex analysis : an introduction to the theory of analytic functions of one complex variable. 3rd ed. New York; Toronto : McGraw-Hill, c1979. [2]
Conway, John B. Functions of one complex variable [by] John B. Conway. [New York] Springer-Verlag New York, 1973. [1]
Priestley, Introduction to complex analysis
Titchmarsh. Theory of Functions
Boas. Primer of Real Functions
Polya & Szego. Problems & Theorems in Analysis
Rudin, Walter. Principles of mathematical analysis. 3d ed. New York : McGraw-Hill, 1976. [2]
Rudin, Walter. "Functional Analysis"
Royden, H. L. Real analysis. 3rd ed. New York, Macmillan ; London : Collier Macmillan, 1988. [1]
Hewitt, Edwin, 1920. Real and abstract analysis : a modern treatment of the theory of functions of a real variable. New York : Springer-Verlag, 1969. [2]
Dieudonne'. Foundations of Analysis
Courant & Hilbert. Mathematical Methods of Physics.
David Hilbert. Foundations of Geometry 2nd English edition, tr. by Leo Unger, publ. by Open Court, 1971. Neumann, Stoy & Thompson. Groups and Geometry [1]
Hardy, Littlewood.
Samuel, "Algebraic Theory of Numbers"
Hardy & Wright
Morris Kline Mathematical Thought from Ancient to Modern Times
Guillemin, Victor and Alan Pollack: Differential Topology. Spivak, Michael: A Comprehensive Introduction to Differential Geometry, Vol. I
Morgan, Frank: Riemannian Geometry: A Beginner's Guide
Milnor, "Topology from the Differentiable Viewpoint"
R. Engelking. General Topology.
Kuratowski. Topology.
Copson. Metric Spaces.
Greenberg, Martin and (?) Harper: Algebraic Topology: An Introduction.
Kelly, General topology
Hardy, Course of Pure Mathematics.[2]
Landau. Differential & Integral Calculus.
Courant & John. Introduction to Calculus & Analysis, vol.1.
Spivak. Calculus on Manifolds.
Feller, Introduction to probability theory
Silvey, Statistical inference
Weir, Integration and measure
Courant & Robins [2] What is Mathematics. Oxford University Press. 1969