The Brain of the Army |Mozg Armii, 1929, by Boris Mikhaylovich Shaposhnikov.
> so take everything you read by him with a massive grain of salt.
As opposed to what? Take everything with a massive grain of salt.
> a lot of his work was written by MI5 ghostwriters, or edited by them.
Who wrote what he should have seen in USSR in 1970s? =)
Between him making fun of Brits, and Brits' own late operations (like magic "novichok" story) amply demonstrating their current ability to construct anything believable, this needs to be taken with an even larger boulder of salt.