There are many, many books on Bletchley Park and its activities.
Try these:
'Unravelling Enigma' by Maurice Freedman
pub. Pen & Sword, Barnsley, 2001
'Enigma' by H. Sebag-Montefiore
pub.Phoenix, Lond.2001
'Codebreakers' by Hinsley and Stripp (eds.)
pub. OUP,1993
'The Codebreakers' by D. Kahn
pub.Sphere,1973
'Enigma' by Robert Harris
pub.QPD, Lond. 1995
The coverage on Bletchley Park has been extensive. I am surprised that there is any more to say on the subject.