Hey I'm not the only Dirk Pitt fan here, great!
One thing that Cussler started doing about the halfway mark was insert himself into the story, like a Hitchcock cameo, you know he'd pop up midway thru the story and help Dirk Pitt with something than Pitt would say something like "btw whats your name?", "Oh its Cussler, Clive Cussler". A bit silly but he's the boss.
My favorites were prob the middle bunch, Treasure, Dragon, Sahara, Inca Gold, his fattest books, all very readable!
Only one of his books has been made into a film so far,
Raise the Titanic, which was the biggest flop ever at the time, Dirk Pitt was played by the late Richard Jordan.
but I recall "Inca Gold" and "Sahara" being particularly fun. "Valhalla Rising" is the most recent and will likely have the order of the previous books in an inside cover.