It is. I picked it up by accident. It is not spectacular, but it is informative. It seems to be based on a lot of different first-hand accounts of the Park, and it does not discuss them too much -- but I think those are interesting in themselves. And I have always had a very unclear idea of what went on there (I know about Turing and the enigma stuff, of course; but how and who and what &c...).

I've read about a fourth of it so far.