The first two thirds of this book—the near-future bits—feel incredibly fast-paced, which always feels surprising in Stephenson’s novels since, as one reviewer put it, he does seem in love with describing things.
The book that that first two thirds reminded me of was Larry Niven &
Jerry Pournelle’s Lucifer’s Hammer, which is perhaps not entirely surprising—it’s a late 70’s disaster novel involving a comet that hits the Earth and the scrambling of various people to survive and even rebuild society. Seveneves is that writ somewhat larger, since it takes the human population and reduces it to a couple of thousand, and it’s from nearly forty years later on, which means it actually gives a lot of women actual agency, even as it recognizes that they need to make lots of babies to restart the human race.
Also (SPOILERS!) they both have cannibals.
The last third does drag a bit; the story is interesting enough—it had some distinct surprises for me at least, though it doesn’t hold a candle to the first two thirds—but yeah, I started to glaze over at the pages and pages of description. It is the “John Galt’s Speech” of descriptions of orbital habitats and the like: even the first time you read it, you only skim it.
Whether you will enjoy this will probably come down to whether you like any of Neal Stephenson’s books at all: if you do, you should certainly enjoy the first two thirds. If, on the other hand, you actually enjoyed Anathem, you might well enjoy the last third as well. Otherwise consider simply stopping when you get to the “Five Thousand Years Later” bit and reading a synopsis elsewhere.