Conspiracy Thrillers
 

I'm looking for a good conspiracy thriller, series or standalone.

I read Upon a Pale Horse by Russell Blake, about powerful government/Bildeberg type groups who wanted to wipe out most of the world's population with a superbug pandemic they'd had cooked up in a lab.

Does anyone have any other recs for thrillers with shadowy groups who have dastardly plans and pull all the strings?

Most of Robert Ludlum's thrillers fit that description, and they're all (IMHO, at least) good.

Try Steven Konkoly.
Also Ramsey's Gold by Russell Blake.
I know there are more but my brain is asleep.

One of the classics was Six Days of the Condor by James Grady (cut to 3 days of the Condor in the movie). Marathon Man was another good one (I thought the book was better than the movie).

Some of Clive Cussler's books from his Dirk Pitt & Oregon Files series fit the bill. The Dirk Pitt titles Vixen 03, Deep Six and Sahara spring to mind.

David Baldacci's Camel Club Series, Sean King and Michelle Maxwell Series, John Puller Series and Will Robie Series.
Apache

The Fifth Horseman by Larry Collins and Dominique Lapierre (1980) was one I liked, but I read it in the '80s, and I wonder if perhaps it will seem a bit tame compared to real-life events that have occured since then.

David Brin's The Giving Plague is an intesting sort of conspiracy story. It's very short, but free.

One that just occurred to me is the Deep Six series by Larry Correia. Definitely heavy on the conspiracy side of things.

The Illuminatus! Trilogy by Robert Shea and Robert Anton Wilson is one I have been meaning to read, not a conventional thriller I think, but it looks like fun to me. Anyone else read it?

Just finished Alex Berenson's latest John Wells book "The Wolves" and it is excellent. Fast paced intrigue. John Wells is ex-CIA now black ops kind of guy. This particular book is a continuation of Berenson's last one ("Twelve Days") so I'd start with that one.
If you want to go back to the very first one in the series, the order is listed on "stopyourekillingme.com". There are 10 in total.

Yes, many years ago. I abandoned it. I honestly wouldn't bother with it.

Read it about 15 years ago, I quite liked it then. Lots of drugs, sex and conspiracies. I think there was a submarine, too. No idea how it holds up.

Seconding Apache's recommendation for Baldacci

If you like action/adventure with your conspiracies, try the Cotton Malone books by Steve Berry. Note these are not always too realistic, but OK for some light reading.

Give Inferno, by Dan Brown, a chance.

Umberto Eco's Foucault's Pendulum is a nice parody on the Illuminati/Freemason type secret society novel. Funny, but there's also a level of suspense.