The Number Devil: A Mathematical Adventure

By Hans Magnus Enzensberger

What Is Mathematics?: An Elementary Approach to Ideas and Methods
Secrets of Mental Math: The Mathemagician's Guide to Lightning Calculation and Amazing Math Tricks
An Imaginary Tale: The Story of √-1 (Princeton Science Library)
Mathematical Logic (Dover Books on Mathematics)

By Stephen Cole Kleene

Schaum's 3,000 Solved Problems in Calculus (Schaum's Outlines)
Handbook of Mathematical Functions: with Formulas, Graphs, and Mathematical Tables (Dover Books on Mathematics)
Real Analysis: Modern Techniques and Their Applications (Pure and Applied Mathematics: A Wiley Series of Texts, Monographs and Tracts)
Sobolev Spaces: 140 (Pure and Applied Mathematics)
Introduction to Partial Differential Equations and Hilbert Space Methods (Dover Books on Mathematics)

By Karl E. Gustafson

The Axiom of Choice (Dover Books on Mathematics)

By Thomas J. Jech

Counterexamples in Analysis (Dover Books on Mathematics)
Lie Groups, Physics, and Geometry: An Introduction for Physicists, Engineers and Chemists
Introduction to Probability Models