Significant pieces of the moon remain in orbit - 'as large are Ireland' - which can't allow that much bombardment. But how big is the moon? I don't actually know, and NS doesn't tell us, but somehow even though it's bigger than I expect, I doubt it's sufficiently big to provide so many meteors that they'll increase the air global temperature to ignite for thousands of years or indeed at all. Some for instances - the moon breaks up into asteroids, some of which rain down as meteors onto earth. The more you obsess over the technical aspects of one thing, the more obvious it is when you skim over another. This has never been NS's strong point, and it's considerably worse now. The summary s quite simple - the moon explodes, earth is sterilised a few people escape into space.The problem with writing hard sf is that getting the details correct really matters, and equally it's very important to show the readers these, rather than just telling them in exposition. The third part is set an arbitrary 5000 years later on, and can be read independently as an epilogue or third part of a trilogy picking up some of the ancestors dilemmas. The first two parts (why two parts there's no sufficient justification for where the part break is - are about 2/3 of the total page count and cover the space of just two years. It's so long (although this review is getting close to having the same trouble) that it's not really one book at all. Possibly it suffers from famous author syndrome whereby compared to early works, no editor has enough power to overrule the author's desire to include far too much verbiage.

And loses quite a few for some inconsistent and sometimes just plain bad writing. A very difficult 'book' to review - it scores lots of bonus marks for innovation.

Seveneves