Memoirs of R.V. Jones, who was Head of British Scientific Intelligence during WW2. His department had to deal with figuring out the technical stuff the Germans were developing and using, especially regarding radio, radar and remote guidance, and devise countermeasures. It also repeatedly touches on the matter of how to collect intelligence info, and how to deal with it. For instance, even after cracking Enigma, the British could primarily use the intelligence gathered that way only as a means to verify other sources; if they had used it fully, it would have clued the Germans that Enigma was cracked and they would have switched to other means of encryption.

Starts a bit slow, but once the war gets going, the book does too.