This series continues to be a solid and consistent read. There are several plotlines going on simultaneously, with one picking up on the spaceship rescues from those outside of time, including relationship angst for Chase, and also the delightful return to Sol. 
 Of course, a return to the Earth and our solar system is roughly on par to returning to Sumeria a few thousand years from now to try and figure out, from scratch, what those people were like. 
 It's really a shame that humanity had a breakdown about 5k years go and anything that wasn't written in stone was lost, or else this little job of trying to figure out what a cell phone is or how the cradle of civilization had gotten to the moon in the first place would have been a much easier proposition. 
 Ah, but our favorite characters *do* have tidbits and hints from the diligent work of previous archeologists, at least, and some names have passed through 9k years relatively intact, the God Einstein not being one of those intact personages. ;) 
 Still, it's fun uncovering our present and our near future through the very distant eyes of these characters, thereby becoming a wonderful mirror to ourselves trying to figure out Sumerian culture or architecture from the scant clues that are left to us. The idea that our pasts, including what we might call our pre-written history, might actually be nothing of the sort. 
 Things fall apart. We could have come from a very advanced past, outgrowing so many kinds of needs, but even if they had all made things to last, the fact is: This is a Very Long Time. Nothing lasts. We just cannot know. 
 I feel pity for Alex and Chase, but pride in the fact that they're trying. 
 This is a very thoughtful novel. Not so exciting as some of the previous ones, but being thoughtful is good, too. :)