I’m a fan of Douglas Preston and Lincoln Child’s books, but Riptide is a book you should skip. The setting, plot, and characters were all decent, but I didn’t buy the villain’s character arc, and as a result I can’t recommend the book. Here’s what Publisher’s Weekly had to say about the book:

The novel suffers from a diffusion of villains as the authors variously demonize the Pit, the Pit’s designer, the crazed expedition leader and the Sword as and from workaday prose and assembly-line characters (a computer nerd, a sexy French archeologist, a righteous minister). Machine-gun pacing, startling plot twists and smart use of legend, scientific lore (including cyptanalysis) and the evocative setting carry the day, however, resulting in an exciting boys’ adventure tale for adults that’s bound to be one of most popular of the summer reads.

I didn’t have a problem with the workaday prose or the assembly-line character, just the character arc which killed the book for me.