I love Martin Gardner's puzzle, math, magic, and philosophy books. I just learned from visiting Clifford Pickover's website about a Gardner book that's new to me: Logic Machines & Diagrams (1958).
From the introduction:
A logic machine is a device, electrical or mechanical,
designed specifically for solving problems in formal logic. A logic
diagram is a geometrical method for doing the same thing. The two
fields are closely intertwined, and this book is the first attempt in
any language to trace their curious, fascinating histories.
I think I need the hard copy.
