Neal Stephenson is presently my favorite author, and so it shouldn't be a surprise that I liked this book. It wasn't perfect, but it was still pretty good! If you have enjoyed his previous novels, you'll like Seveneves.
I liked that I had no idea what the title of the book meant until the last third or so of the book. That was a cool twist, and the title was definitely the right choice.
Character development is always great in Stephenson novels and this was no surprise (with one minor exception - Aïda sorta came out of nowhere, but I'll allow it). I really found myself rooting for some of them, and despising and wishing the worst for others. And for what it's worth, I pictured Doob the entire time as Neil deGrasse Tyson - I've read that he was supposed to be Carl Sagan (and I can sorta see that too) - but in my head he was NDT and since I like and respect NDT I am not conflicted about this apparent mistake.
Lastly, the plot really is pretty engaging. It takes a while to develop, but I didn't mind as it was entertaining the whole time.
This book is science fiction, and it starts out with a huge leap where something completely out there happens and only the briefest of explanations is given; this is notable because at many points throughout the book (and at the expense of the plot often) long explanations are given for things that the reader probably doesn't care about. I mean, it's cool that he put so much research into being technically accurate, and I can appreciate putting rigour into the plausibility of the story, I'd rather have some appendices full of actual math and diagrams that were optional rather than trying to explain things like orbital mechanics and spherical coordinate systems in paragraph form. He gets a bit lost with it sometimes.
I also thought that the end was too abrupt. That said, the book could have ended about three quarters of the way through with a fairly satisfying climax. Instead, it doesn't end there, and as the back cover points out (which was a spoiler I didn't care to know) zooms forward 5,000 years and then goes basically nowhere for way too long. I thought to myself more than once that I should just put the book down and never finish it. But then suddenly it picks up again, but I realized that there were only fifty or so pages left in the book and there was so much more to cover. And then it ended. I found myself wishing that it was broken into two parts - one that ended where I thought it should have, and then another volume for an expanded and lengthened version of the rest.
Not my favorite Stephenson story (the Baroque Cycle is my jam, yo), but definitely good. Even a flawed Stephenson novel is better than most anything else out there. I'll probably reread it in 10 years or so once it fades some.
I can't give this a 5 out of 5 star review, but it's better than a lot of books that I call a 4. Call it 4.5/5.