What a strange book, but not so strange considering the author's education. Reynolds has a PhD in Astronomy and worked in the European Space Agency until quitting for full-time work as author. (Read his Revelation Space series, and you'll see how good he is at hard sci-fi.)
This one, however, weird. I didn't know what I was reading at first. Three masted wooden sailing ships, exploring the fjords of Norway? Steam-ships doing the same, but in the Pacific off Patagonia? Airships a la steampunk?
But then the sci-fi creeped in. Were these simulations? Holo-deck? What was the reason, though? Reynolds cleverly introduced the conflict(s), without insulting the reader's intelligence by simply telling us what the dealio was. Nicely done, sir.
I guessed early that Coade was a computer code, or could be, yet the author still didn't confirm till much later, which was nice. Kept me guessing. Ada threw me, so that was nice. And Coronel Ramos was well-done, one of my favorite characters, not just in Eversion.
When the reader finally is brought to "reality" s/he can see where the earlier simulations paralleled (that's not the right verb, but I can't find one now) what the crew actually were going through. Spelunking, diving, water, small passages, claustrophobia. And finally: Death.
Eversion, btw, despite the squiggly red lines under the word as I write, is an actual word, with many definitions, including scientific ones. And this won't ruin the novel (thus this paragraph outside my spoilers): Eversion is the act of turning inside out, scientifically if you flip your upper eyelid up, that's eversion of the eyelid (and gross). If you want to really get deep into the math of eversion, way down a rabbit hole, go here to discuss sphere eversion with other 50lb-heads.