Laurence Dwight Smith —Cryptography: The science of secret writing — Dover, 1943, 164 pp. ISBN 0-486-20247-X
This short book (164 pages or so) presents the basic methods of (non-modern) cryptography: pen-and-paper cryptography by (simple) substitution and transposition, and elements of frequency analysis. The book isn’t bad in itself, and though it feels a lot less erudite and fun than Martin Gardner’s Codes, Ciphers, and secret writings, it is still worth a read as it covers many methods of transposition.
One must also remark that despite being written during the second world war, the book does not discuss mechanical devices at all (for they existed for sure) and is deliciously oblivious to the problems of “real” cryptography—but one can hardly complain as Bletchley Park was then classified and remained so a long while after the end of the war.
Nonetheless, worth a read.