It's an opinionated tale of someone actually doing the business of catching spies.
Even better for the HN crowd, the author was an engineer so there's some tidbits about just how advanced spook technology was even in the 50s and 60s (i.e. using acoustics to lift encryption keys through embassy walls as they were being typed)
The more factual parts are genuinely dangerous if not for the late date it was published.
The more speculative aspects like the authors' judgement of Roger Hollis is genuinely really weird. We will probably never know the truth, but if he wasn't a spy there are some genuinely abnormal correlations to be explained. If you're familiar with the case the Australian intelligence analyst Paul Monk gives a fairly strong case that even if the official story on Hollis isn't wrong, it is wildly inconsistent and economical with the truth.
Wright is a bit of a loose cannon, but the late Chapman Pincher wrote an enormous book on effectively everything publicly known about the (at the age of about 100 no less) which is much more methodical.
There was a IWP panel about the case a few years ago; some evidence is so murky that some analysts were, even with a fastidiously planned and documented "argument map" to summarize the known evidence, joking about resorting to sending a freedom of information request to the GRU.
It's an opinionated tale of someone actually doing the business of catching spies.
Even better for the HN crowd, the author was an engineer so there's some tidbits about just how advanced spook technology was even in the 50s and 60s (i.e. using acoustics to lift encryption keys through embassy walls as they were being typed)