This starts off as being just an explanation of how geology works — deposition over time, the way rocks are transformed and eroded, etc, etc. The last couple of chapters start getting into the stuff I’m really interested in: how material remains of humans might weather and last, to be found for potential future alien archaeologists. I didn’t really love Zalasiewicz’s attempts at sci-fi, with his commentary on these alien archaeologists/anthropologists and what they might think. Like most people, he sticks too close to the way humans think, and doesn’t try and figure out what the alien equivalent of “it must be for ritual purposes” might be.
(For instance, imagine a society entirely driven by scientific experiment. Instead of interpreting everything as ritual, they’d assume it was an attempt to find out what would happen if you did x and y! And then they’d try it for themselves! Doesn’t that sound interesting as an idea?)
Mostly pretty standard stuff, but the last couple of chapters were worth it.