It took until my e-reader told me I had read 73% of the book to understand why Gerlis bothered writing this book at all.
The historical facts are well known, leaving no suspense. The writing is bland and expository. The characters are such cardboard cutouts I frequently had to thumb backwards to remember who was who.
Then, finally, at the 73% mark the titular protagonist performs the one decent act in the book, which naturally marks him for death.
So I guess that’s the purpose: spying is a nasty, dirty business that can only end in misery and death. Much like this book.