Books like The Ultra Secret
Frederick William Winterbotham
The Ultra Secret is 286 pages, about 5 hours 15 minutes at 250 words a minute.
12 books to read next
How long each takes
The Hut Six Story 6.0 h 
Fatherland 7.1 h 
Enigma 7.5 h 
Going Solo 3.8 h 
Between Silk and Cyanide 11.2 h 
Cryptonomicon 16.8 h 
The Great Escape 4.8 h 
The Eagle Has Landed 7.0 h 
Code Girls 6.9 h 
The Jungle Is Neutral 7.3 h 
Bomb 4.9 h 
The Key to Rebecca 6.5 h Bar height shows length. Estimated at 250 words a minute.