I liked the book, actually, but the science is wonky as fuck the whole way through, not just at the end. Like half the world-building of the book is that they would go through all the trouble to build a giant dome city on the fucking moon, but then just not pressurize the atmosphere so they could have a standard nitrogen-based mix to avoid literally every issue that comes from living in a pure O2 atmosphere. The ISS right now operates under a standard Earth atmospheric mix under pressure. We haven’t used pure oxygen since like Apollo 1 in the 1960’s (precisely because of Apollo 1’s pure O2 atmosphere catching fire and killing everyone). Weir did a bunch of research on stuff like how an automated lunar mining machine’s cooling system might work, but also didn’t bother researching basic shit like what astronauts breathe. Yet, I still found the book oddly charming somehow. Weird how that works.