Martin Gardner Reading List: Required!
Martin Gardner wrote a lot of interesting books dealing with recreational mathematics or science. Without any hesitation, I recommend all of these, sorted by year:
 1956, Mathematics, Magic and Mystery
 1957, Science Puzzlers
 1957, Fads and Fallacies in the Name of Science
 1958, Logic Machines and Diagrams
 1960, The Annotated Alice
 1964, The Ambidextrous Universe: Mirror Asymmetry and TimeReversed Worlds
 1975, Mathematical Carnival: A New Roundup of Tantalizers and Puzzles from "Scientific American"
 1976, The Incredible Dr. Matrix
 1978, Aha! Insight
 1981, Science: Good, Bad, and Bogus
 1981, Entertaining Science Experiments With Everyday Objects
 1982, Aha! Gotcha: Paradoxes to Puzzle and Delight
 1984, Codes, Ciphers and Secret Writing (Test Your Code Breaking Skills)
 1985, Magic Numbers of Dr Matrix
 1986, Entertaining Mathematical Puzzles
 1987, The NoSided Professor and Other Tales of Fantasy, Humor, Mystery, and Philosophy
 1987, Riddles of the Sphinx
 1987, Time Travel and Other Mathematical Bewilderments
 1990, More Annotated Alice ("supplement" to The Annotated Alice)
 1991, The Unexpected Hanging and Other Mathematical Diversions
 1991, Fractal Music, Hypercards and More
 1994, My Best Mathematical and Logic Puzzles
 1995, Classic Brainteasers, Sterling Publishing
 1996, Weird Water & Fuzzy Logic: More Notes of a Fringe Watcher
 1998, Martin Gardner's Table Magic
 1998, Mathematical Recreations: A Collection in Honor of Martin Gardner
 1999, Gardner's Whys & Wherefores
 1999, The Annotated Alice: The Definitive Edition
 2001, A Gardner's Workout: Training the Mind and Entertaining the Spirit
 2001, Mathematical Puzzle Tales
 2001, Did Adam and Eve Have Navels?: Debunking Pseudoscience
 2003, Are Universes Thicker Than Blackberries?: Discourses on Gödel, Magic Hexagrams, Little Red Riding Hood, and Other Mathematical and Pseudoscientific Topics
 2007, The Jinn from Hyperspace: And Other Scribblings—both Serious and Whimsical
And this is only a partial list! Be aware that many of them have been reissued under new names, especially recently as part of a new MAA series.
