It is a short book but I particularly found fascinating the re-interpreted Genesis chapters towards the end.
While it's an interesting theory, I'm not convinced it's entirely the whole truth. It was written several decades ago, and I still consider the astronomical rather than geological (even though they can be intertwined) hypothesis as more probable. That said though, there is an agreeable perspective of our history.
The main thought that comes from reading this book personally is that the Earth is a special place, and the idea that it periodically suffers cataclysmic events reinforces the idea that it is an important place of learning. While we have no concrete proof that other similar planets conducive to life exist, we can suppose that they do. There is no guarantee however that they undergo the same frequency of periodic cataclysmic events, if at all. Other solar systems may not have to worry about the asteroid fields or Oort clouds. It could be that Earth is unique in that it is conducive to life, but also undergoes regular and periodic struggles. Other planets may evolve without any astronomical issues, but in doing so miss out of the struggles and experiences that people here have to endure.