The nice thing about Cussler novels is that you get exactly what you paid for (The novels are pretty cheap). There are rarely (bad) surprises. And even though the characters from the NUMA series are generated from the same template as the characters from the older Pitt series I prefer the newer, slightly fresher ones.
The plot follows the usual archetype. Despite there being no surprises, or maybe because of it, the novels offers some good hours of quiet relaxation. No active thinking needed. The books has served its purpose.