The Banach-Tarski Paradox, Cambridge Univ. Press, 1985, paperback. More info
Second edition of the book, by G. Tomkowicz and me, is now (Aug 2015) at the publisher (Cambridge U Press). Contact me for notification upon publication.

The SIAM 100-Digit Challenge: A Study in High-Accuracy Numerical Computing, with D. Laurie, F. Bornemann, J. Waldvogel, SIAM, Philadelphia, 2004, 300 pp. More info.

VisualDSolve: Visualizing Differential Equations with Mathematica, with Dan Schwalbe, Second edition, with Antonin Slavik and Dan Schwalbe, e-book, Wolfram Research, 2009, <http://www.wolfram.com/books/profile.cgi?id=7543>

Mathematica in Action, third edition, Springer-Verlag, 2010, paperback. More info.

A Course in Computational Number Theory, with D. Bressoud, 2000, Key College Publishing and Springer, hardback. Named one of the ten best math books of 2000 by the American Library Association.  More info.

Which Way Did the Bicycle Go?, with J. D. E. Konhauser and D. Velleman, Math. Assoc. of America, 1996, paperback.

Old and New Unsolved Problems in Plane Geometry and Number Theory, with V. Klee, Math. Assoc. of America, 1991, paperback.

Animating Calculus, with E. Packel, Springer/TELOS, 1996, paperback. More info.

The Mathematical Explorer, Wolfram Reseaerch, Inc., 2001, electronic book/software More info.