Since the books have the same protagonist, would the work of Tom Clancy be considered a series? If so, that’s my favorite. Tom writes with high granularity, ie, visualization-enhancing descriptive depth. It’s like a movie in your mind.
Sure, most of his books are continuous -- at least, I think they were. I stopped reading them some time back. I think "Without Remorse" was the last one I read.
I would definitely consider them a series. Even when Clancy departs from the timeline -- as in Without Remorse -- he manages to tie it in to the narrative. In WR, Jack Ryan has a cameo as the teenaged son of the Baltimore cop investigating ... the stuff (I don't want to give spoilers).
My big beef with the Jack Ryan series is that Clancy fell prey to ever-increasing expectations -- each book had to end with a bigger bang than the last, to a degree that began to border on the absurd. To his credit, I think Clancy saw that -- which is why his latest books are prequels (Red Rabbit) or following another tangent (the Rainbow Six series). Because, let's face it, there isn't much of anywhere else to take the character of Jack Ryan unless Clancy wants to crown him the Messiah.