Hello Adriano,
Searching for something else, I came across your old posting. Yes, I have read the book and it is definitely written by someone who has knowledge of and access to nightfighter history. He certainly had access to the archive of the Strüning family. It is a good read but not a reference work with Flugbuch copies etc. A lot of dialogues between Strüning and comrades is another feature I can't explain unless the author followed Strüning during his career and made notes of his speech and thoughts
I have checked some statements about the whereabouts of Strüning when specific events occurred and discovered several discrepancies.
General conclusion: the author has written a sort of biographie with a lot of acknowledged facts as a basis but filled the pages with generally known developements in the nocturnal air war 1940-1945 and invented dialogues. For 15 Euros nevertheless a good read.
Best regards, Marcel