I see now why it's called Sahara, because the writing is as dry as that desert.
I have never before read a book where the author thought dialogue was the exact same thing as exposition dump. I mean, I've read books approaching that mistake, we all have, but this took the cake. This reached parody levels.
The book got off to a good, promising start - one that never continued - and the action scenes are - serviceable, I guess? But the dialogue, oh god the dialogue. Clive does not know how to write dialogue. It is completely interchangeable, painful exposition dump after painful exposition dump.
Clive thinks it necessary to actually tell us, repeatedly, not only what is happening but what has JUST HAPPENED even though WE WERE THERE.
*characters do something significant/event happens to them*
One character to the other: "So this just happened, eight seconds ago"
Other character: "Please explain further. Do it not like I'm your friend but like I'm your examiner and you're submitting me your report on it."
First character: "Glady. Let me tell you what we both just experienced. Then I'll answer your questions about it - despite the fact you already know the answer - and I'll answer them again. Then later on we can switch roles and do the same thing again."
Second character: "I love that we're each other's soundboards. It makes me feel so special."
Because this doesn't just happen once. It happens continuously, about the same things. Clive must think his audience is dumber than a box of rocks. His characters talk like they've suddenly turned to the camera and engaged in monotone fourth-wall breaking delivery. I've seen more charismatic, naturalistic dialogue in a engineering survey. This book would be so, so much better if all dialogue was expunged and Dirk and his presumable friends - and enemies - were all mute puppets lurching across the desert and attempting cavalier smiles/Machiavellian sneers at the camera.
I cannot express how dry this novel is. How repetitive it is. How artificially drawn out the length is. How dull the relentless exposition is (cut it out and the whole novel would probably be halved in size, and significantly better for it), not to mention how they made what should have been an against-the-clock doomsday plot into a boring academic treatise with zero tension or excitement. Clive's characters drone on so much about the technical specifics of the disaster about to befall humanity - and do it so often, and in such academic detail - that you just want to fall asleep on the book and hope the apocalypse actually does arrive so at least then people might show some emotion. Then again, they'd probably just say things like, "I am feeling sad right now. Because last page this happened and then this happened and it happened because..."
Dirk is clearly supposed to be a Bond figure, but he comes across as a banal snob with artificial charisma and there is zero sense why the woman suddenly falls in love with him despite her having barely any significance to the plot (and not much more presence - she drops out of the novel for very large periods of time to no effect, and is, of course, saved by the supposedly dashing Dirk). We're told Dirk is a handsome rogue but he talks like a charmless, unpleasant, arrogant bureaucrat who was raised by computers.
Then again, so does everyone else in the novel, bar the occasional character which is the standard template with an added stereotype on top. Crikey! Blimey! Top hole!
A few things more can be added to this novel: Can-never-fail protagonist, can-never-succeed antagonist, white saviour complex (saving other white people and massacring literally hundreds if not thousands of evil brown people, carefree protags acting as though they were completely in the right to be there in a foreign country, despite no sanction for the politically explosive behaviour, and barely a damn given about the locals - even leaving them all behind in a slavery rescue (one with Holocaust allusions) to fend for themselves, because dammit, we only care about OUR people!), plentiful casual sexism (more bearable if there was any charm to any of the characters, and if the woman wasn't simply a pointless and ineffective fawning damsel, despite her intellectual listed credentials), and, as mentioned, no personalities anywhere to be seen.
On top of that, a sporadic Confederate-era mystery that pops up like three times in the plot and has nothing to do with anything else at all, and the conspiracy at the end that wraps it all up is absolutely inane, at least it is the way it's described. It involves one of the most famous people in history's wife sitting next to them for hours and not recognising that they're not their husband but a random person. Just like the hundreds of others in the same room not recognising the swap. The same wool is pulled over the eyes of dozens, hundreds, thousands, millions of others.
Again - no charm. No "oooh, wow!" Instead we just get Ben Stein reading this textbook to us as we fall asleep, and then as soon as we wake up he does it again. And again. And again.
Drier than the Sahara. And a great example of what I'd call an "airport novel".
P.S. It's a small example but to me it sticks sorely in my brain. Clive (or, worse yet, his characters), at several points in the book, tells us how far something is in kilometres, then immediately tells us what that is in miles. Take from that what you will.
P.P.S. Clive Cussler himself is in this book. I've heard he appears in many of his books. It's lame, and he actually harms his own personality by making himself one of his own characters.