Thought of another one for you. The "Sean Dillon" series by Jack Higgins. Ex-IRA enforcer that goes to work for British spy agency. Older series, been years since I read them, but good stuff.

Mentioned above but I’d like to second (or third) the recommendations:
1. The Gabriel Allon series by Daniel Silva
2. Anything by Bernard Cornwall: Sharpe; the Saxon Chronicles; the Arthurian series; the longbow series (Agincourt, etc.)

Stephen Pressfield has written a number of historical fiction novels based on real characters: Gates of Fire about Thermopylae; The Tides of War about Alcibiades; The Virtues of War about Alexander the Great; and one great pure history book, The Lions Gate, about the Six-Day war in 1967. He’s a great writer.

I’m surprised I haven’t seen her a recommendation for the many books of Stephen Hunter with his heroes Bob Lee Swagger and his dad Earl. Great action novels with the most realistic gun action descriptions you will see anywhere.

Already mentioned, it's serious science fiction, Hyperion.
I rate it among the best science fiction I've read.

Already mentioned, but fun fantasy, Harry Dresden Files. Fun that I got it free from the library as an ebook and then ran through them all (something like 15).

I’ll add another book series as well, the Captain Alatriste series from Spanish author, Arturo Pérez-Reverte. Alatriste is a 17th century swordsman and soldier. Pérez-Reverte is a brilliant writer, and the translators he works with do a really nice job of bringing his books to English speaking countries. He has written books other than historical novels, but the thread is about book series. I really, really like this author.

James Jones;

From Here to Eternity
The Thin Red Line
Whistle

For fantasy I really enjoyed the Mistborn trilogy by Brandon Sanderson. Extremely interesting magic system. As an example, one person may be able to inject flakes of tin and see/hear much better. There are other metals and individual abilities, usually only one per person.