Martin Gardner books in order
12 books in the catalogue, about 60 hours of reading in all; the shortest takes 2 hours and the longest 13 hours.
12 standalone books in the catalogue.
Standalone books
In the Name of Science 6.7 h 
The Scientific American Book of Mathematical Puzzles & Diversions 3.0 h 
The 2Nd Scientific American Book of Mathematical Puzzles & Diversions 3.8 h 
The Ambidextrous Universe 5.4 h 
Codes, Ciphers and Secret Writing 1.9 h 
100 Great Science Fiction Short Short Stories 5.0 h 
Aha! Insight 3.3 h 
Isaac Asimov's Masters of Science Fiction 5.3 h Mathematical Circus 5.0 h 
Mathenauts 5.5 h 
My Best Mathematical and Logic Puzzles 1.5 h 
The Colossal Book of Mathematics 13.3 h