This is the third and final collection of puzzle columns that I contributed to Isaac Asimou's Science Fiction Magazine over a period of about ten years. The format follows that of two previous anthologies: Science Fiction Puzzle Tales (1981) and Puzzles from Other Worlds (1984).

Each chapter poses a problem answered in the First Answers section. The solution in turn raises another problem that is solved in the Second Answers section. This may suggest a third question, and in several instances there is a fourth. Material has been added based on letters from readers of Asimov's magazine, material from my files, and suggestions from others listed below.

Many of the problems lead into nontrivial regions of mathematics and science. Whether or not these puzzles have deeper roots, I hope readers will find them entertaining, and enjoy the opportunity to exercise their wits.

I wish particularly to thank Peter Ungar for going so painstakingly through the manuscript and adding fascinating new material, and Anneli Lax for her superb editing and production work. I am indebted also to Basil Gordon and Richard Guy for numerous corrections and excellent suggestions, and to Peter Renz for suggesting the MAA as a publisher, finding ideal illustrators, for general supervision of the book's production, and for providing valuable input in many ways.