Brain-teasing puzzles by Martin Gardner, including "The Returning Explorer," "The Mutilated Chessboard" and "Scrambled Box Tops," are challenging math games for adults. Sam Loyd and Henry Dudeney also offer challenging math puzzles that are appropriate for adults.
Between the 1950s and 1980s, Martin Gardner developed a series of math puzzles that he included in his column in the Scientific American magazine. Collections of his puzzles are available in various print publications. Gardner's collection of puzzles called "My Best Mathematical and Logic Puzzles" contains 70 of his most popular puzzles, as well as their solutions. He also has several recreational math books for adults.