I've always enjoyed his books[1] as sort of a "Spy thriller done right" antidote to Fleming's "Fantasy Spy Thriller".
[1] I think "Cobra" was the last one I read, and enjoyed it immensely.
"In 1963 MacLean decided to retire from writing, saying he never enjoyed it and only did it to make money."
https://en.wikipedia.org/wiki/Alistair_MacLean
The retirement didn't take, he ended up producing more.