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I'm a HUGE Neal Stephenson fan -- I've read almost all his novels (excluding the seemingly-disowned "The Big U"), "Snow Crash" and "Anathem" are favorites of mine and I've enjoyed the rest to greater ("The Diamond Age") or lesser (the disappointing conclusion of the Baroque Cycle, "The System of the World") degrees. So, you should know going in to this that I have a pretty strong bias toward his writing: STEM badasses that solve crises with insight, (often reluctant or inadvertant) bravery and decisive action. Basically, imagine Bruce Lee, but if he used math instead of kung fu*.
As a sci-fi guy, any book that starts with "The moon blew up without warning and for no apparent reason" is starting with a massive head start for me (rather shockingly, the reason of the moon's destruction is a complete non-issue). Especially since I get to learn a lot more about orbital mechanics, robotics, whips, and a wee bit about genetics** during a great read. And a great read it is -- the first 2/3rds are a nonstop race to save humanity from the impending multi-millenial Hard Rain of the shards of the moon. This is shown mostly from the perspective of various 'nauts on the ISS, with only glimpses of the action down on Earth -- glimpses that are not always what they first seem.
The final third? A look at where that race led, and its unexpected consequences 5000 years later. This is a fairly strong phase transition from near-future hard sf to more speculative far-future sf. Skipping ahead 5000 years generally means you leave all your previous characters behind***; Stephenson cleverly has them remain in the legacies that they left to their descendants: legacies of the cultural, video and genetic varieties.
As usual with Stephenson, when I finished I wanted to spend more time with the world and characters he'd created. For me, this is a key part of the enjoyment of a great book -- wanting to see what they would do next, thinking of consequences had they made different choices. The book flew by, in spite of its length, leaving me thrilled at the ending (and the journey to get there) and disappointed that there wasn't more.
* Or wushu, if you're being pedantic. Which I usually am.
** I'm waiting to hear from my biologist buddies if I learned or mislearned.
*** Unless you're Frank Herbert