I've read his entire Dirk Pitt series. I really enjoy them. Part way through his series, he began inserting himself in a scene. People liked it so much that he has done it in each book since. He's admitted that he's running out of ideas, but his son is taking over the series. The last couple have been written with him.

I've also read his Sea Hunter books. They're about ships that his real life, not for profit company, NUMA (also the fictional government agency he created for his Pitt and Austin novels) have found and/or raised from the sea beds. There is also a television program of the same name. I wish they'd put those on dvd; they're very informative for anyone who enjoys maritime history.

I'm currently reading Blue Gold, which is his other NUMA Files series. So far, it reminds me a bit of the Pitt ones, but with a little less action. However, I'm only about 100 pages in.