For a first - time reader, 'Raise the Titanic!' is a good choice. It's a classic Cussler novel with a straightforward yet thrilling plot. You get introduced to his style of adventure writing.
I would also recommend 'Sahara'. The vivid descriptions of the desert setting and the engaging characters like Dirk Pitt make it an easy and exciting read for someone new to Cussler's works. It gives you a taste of the action - packed adventures his books are known for.
Perhaps 'Iceberg' could be a good pick too. It has a great mystery element as the story unfolds around an iceberg that holds more secrets than meets the eye. The story is full of suspense and adventure, which is typical of Cussler's novels and would be a great introduction to his writing.