This has been on my shelves for way too long. I've discovered that the best way to manage - physically and electronically - is to add to my to-read tag in Goodreads, so things don't get forgotten.
In The Thrilling Adventures of Lovelace and Babbage, Sydney Padua mentioned several times that "The Difference Enginge" sounded much better than "The Analytical Engine", and so she used that in her dialogues even when it was strictly incorrect. Likewise, "Enigma" is a much better name than "Teleprinter" or "Geheimschreiber", or "Fish" (the generic name assigned to its transmissions by Bletchley Park), and so Paul Gannon sets out to put the balance right. Interestingly, both Enigma and Fish decrypts were labelled "Ultra", so in the intelligence reports there was no obvious distinction between them, although the material would generally be of a different type and style - the teleprinter was used for longer, strategic reports and orders rather than field-level updates.
There is some historical background on British codebreaking efforts and some basic information on the development of teleprinter and non-Morse technology. A common thread with Enigma is the flawed use by operators, though there were also technical issues both with the encryption scheme and wireless transmission and reception which allowed Bletchley Park into the code. Max Newman and Ralph Tester were assigned to work on the Fish signals; Turing played no part directly, although his enthusiasm for Post Office engineer Tommy Flowers' work may have been an indirect influence, countering various bureaucratic aspects. An electro-mechanical machine, the (Heath) Robinson, was built in part because of managerial doubts over the use of electronic valves, but eventually Flowers' persistence proved its value, with Colossus immediately producing positive results and having reliability in excess of expectations. There is some doubt as to how many characteristics of a "computer" Colossus had - for example it could not do if/then/else-style branching; on producing a particular output, an operator would choose what instructions (program) to run next. Nevertheless Gannon is determined to set the record straight over ENIAC not being the first; and also to point out that there are still some documents from the period that are withheld (thought likely to refer to general cryptanalytical techniques rather than any technological details).