I see it as 3 books, the first two with the race towards saving mankind from extinction, and the third one the future after 5000 years. No matter how implausib

I see it as 3 books, the first two with the race towards saving mankind from extinction, and the third one the future after 5000 years. No matter how implausible you find that the moon blow up and the fragments did a dance that ended 2 years later, but the third part was a solid block of suspension of disbelief, specially for the genetic and psychological/sociological aspects of it. I don't know, if the initial phrase was "the moon grow legs and walked through the sky", it would had been more plausible than the third part of that book.