Hello,
Prien's book is called "Messerschmitt Bf-109 im Einsatz beim Stab und der I./Jagdgeschwader 27" and there are 3 parts. (3-teilige Chronik)
I have the german version of the book.
http://www.jagdgeschwader.net/index.html (click on Jagdgeschwader 27)
Regards
pilot05