I've always loved the writings of Martin Gardner, who turned 95 this week. He has long been the best known recreational mathematician. He has written on many different topics, but most of his writings focus on puzzles and puzzle solving. He has written over 70 books, including a puzzle and essay collection that was released this month.
Here's a good article on Gardner's career.
A few of Gardner's puzzles.
My favorite article by Gardner is a very early one (from 1956) which introduced me to the wonderful world of flexagons. They were invented at Princeton in 1939 by a graduate student, Arthur Stone. A "Flexagon Committee" that included fellow graduate students Richard Feynman, who went on to win the Nobel Prize in physics, and Bryant Tuckerman, was formed.
I first made flexagons with my dad on the kitchen table, but later started making them at school (this was fifth grade) during boring classes. Sometimes I would sell them, and use the money to buy junk food at lunch.
This picture comes from a great, comprehensive site on flexagons.
The Wikipedia article doesn't provide much information about flexagons, but it does show how to make tetraflexagons and hexaflexigons.
There area number of technical articles on flexagons. This one provides a good overview.
There are many videos of flexagons online. This one is silent, but has some pretty nifty flexing.
Gardner's "The Annotated Alice" is terrific. It provides detailed information on the many obscure jokes and references in "Alice in Wonderland" and "Through the Looking Glass". The "Definitive Edition" contains "The Wasp in the Wig" , a chapter that was left out of "Through the Looking Glass".
Amazon has some interesting editorial reviews of this.
A Gardner bibliography: