I learned a number of things while reading this book. The first and foremost thing that stuck in my head, however, is that supercavers are completely, 100%, absolutely bat-shit crazy. Caves are cool. I've enjoyed some very guided visits to some of them, and to a certain extent, I can see the appeal of doing a little exploring on your own, to see where this passage goes. But to deliberately and repeatedly put yourself through the torture of the kind of intense cave exploration going on in this book? I just can't wrap my head around it.

I really enjoyed this book, though, and I did find it quite gripping. It had the advantage of being neither fiction nor very well-known non-fiction, in that respect. When you're reading a novel, while there are certainly twists, and some authors are better at surprising you than others, but there's a certain narrative structure that you expect, and certain conventions that you expect. Usually, you can guess which characters are at risk of dying, and which are crucial enough to the story that you're confident in their survival (except in those rare instances when you're wrong, and it's almost like a physical blow). Because this was not fiction, I didn't have that sense. Any of these people could die at any moment, and a number of them did, which definitely contributed to the thriller feel this book had. Furthermore, because supercaving is not a field that I'm even remotely familiar with, it wasn't a non-fiction book where you know the outcome and are just reading for the details. I didn't even know going into this which of the two caves would turn out to be the deepest, so that also kept it very engaging.

I won't spoil it, even though you can probably easily find the answer, because I quite enjoyed reading this book without knowing, and I wouldn't want to take that away from anyone else.

I will say, though, that I find the human arrogance in this book a little weird, though. Specifically, the fact that it repeatedly talks about how finding the deepest cave will be the last great discovery on earth. And I just kinda go, really? How can anyone be confident in that assertion? Does anyone honestly think that we've learned everything there is to learn about this planet? Because seriously, I don't think so. There's plenty of ocean left to discover, we're still constantly finding new stuff in rain forests, and even these incredibly deep caves barely scratch the surface of the earth. We haven't come close to touching any of the stuff that's actually at the centre. So to say that there's nothing left to discover is simply preposterous.

Hell, even the absolute assertion that it's the deepest cave seems a little silly to me. It's often compared in this book to Everest, and for good reason, except that there is a difference between mountains and caves. I think it's safe to say that we have in fact explored enough of the earth's surface to know that we have found all the mountains, and Everest is the tallest. There are no more hiding around a corner, so until there are some major geological shifts, I'm confident in the assertion that Everest is the tallest mountain on this planet. One way that caves are different is that they're much less obvious from surface level. On the surface, a massively huge supercave can appear to be little more than a small hole in the ground. One of the caves discussed in this book is in fact just that. So I'm not sure we can necessarily declare that there aren't a few others kicking around that we simply haven't twisted our ankles in yet. I realize that certain conditions are generally required for a cave, and a supercave in particular, so that does theoretically narrow down the possible locations, but I just don't know that I'd be so confident in saying that the deepest one we know of at this time is absolutely and forever the deepest. Even the cave that didn't "win," so to speak, in this book, still has the possibility of being deeper. There's a proven water flow; the people simply haven't figured out how to follow it all the way. Maybe they never will, but maybe they will. Or maybe someone will find another one that goes even deeper.

In any case, like I said, the notion that we've now discovered the last big thing to discover on this planet is just so ridiculously arrogant to me, but it didn't take anything away from my enjoyment of the book.