I couldn't agree more - a thoroughly gripping and intellectually stimulating series - indeed, it was that rare thing, a superbly acted, intelligent and sometimes thought-provoking TV series. When I first saw it, in the late 1970s, as a teenager, I was utterly absorbed, nay transfixed. And Patrick McGoohan was simply sublime. Prompted by your avatar, I watched the (stunning) intro again on You Tube this evening, and am debating watching a few episodes. Will succumb shortly, I expect......
I applaud your excellent taste; it is one of my all time favourites, too.
Have you ever taken a look at Martin Cruz Smith's "Arkady Renko" series? The first three books, "Gorky Park", "Polar Star", and "Red Square" are all excellent. The fourth, "Havanna Bay" is less good, but not too bad. The fifth and sixth in the series "Wolves Eat Dogs" and "Stalin's Ghost" are a return to excellence. Avoid the seventh entirely. It just simply isn't up to the standard of the others.
The very best thrillers manage to excel by offering both a well-plotted narrative along with solid character development.