It starts out briskly, with an interesting premise. A spy satellite crashes to earth, but not before taking pictures of something in Eritea that a lot of people find interesting. A renowned geologist-adventurer soon finds himself in the thick of conspiracies trying to find what some believe to be a motherlode of diamonds, and other believe is much more.
Jack Du Brul knows how to get you hooked, but the book-killer is that the ending is incredibly weak. Not only is the secret a cliche, it's explained away rationally, by means which are implausible at best. There really isn't anything world-shattering about it, which makes some of the foreshadowing ring hollow. It feels like he just included the "much more" on a whim, because he underdevelops it tremendously. What's left is a pretty dull reason for all these people to get worked up about, especially the main villain. Why didn't he just go in legitimately and try and obtain it?
If the writing were any weaker I'd give it one star because of that, but it's paced smartly, with enough realism and difference to entice you. Just expect to shake your head at the ending.