For me, the essential element is that the author used to be an actual spy. Write what you know, as they say. In addition to the entertaining story, I get to guess what is being fictionalized that couldn't be put in non-fiction due to legal restrictions.
This year I read the four books of
Alex Dryden, apparently late of MI6.
By the fourth book, his near-obsessive (if justifiably so) dislike of Vladamir Putin, and of American security contractors, gets just a wee bit repetitive, perhaps explaining why book 4, the latest in the series, has not been published in the US. After getting Book 2 for free from Amazon, and Book 1 and 3 from Overdrive via the library, I plunked down £4.99 to
a British bookshop for the experience of knowing I was one of the few Yanks reading the whole series.
Good author? I think so. The first couple books got great reviews.
P.S. I just noticed that my link immediately above now says you can't buy the book if you live in the US. It didn't say that when I bought it. Googling shows that you can get it
slightly cheaper at a Swiss web site, and without the IMHO ridiculous idea that you can't buy a book, written by a living breathing royalty collecting author, unless it is published in your country.
P.P.S. If I was going to buy many eBooks, instead of getting them from the library, the idea that you have to either leave money on the table, or check web sites around the world to find the best price -- would drive me bonkers. And as far as I can tell, there is no good eBook price check web sites. I just tried two of them. inkmesh.com didn't even list this book, and luzme.com only has two vendors, even though there appear to be many.