I've shied away from some of Neal Stephenson's later co-written works. But peeking at the first few pages at Barnes & Noble hooked me… so I went home and bought the book from Amazon. (No brainer: $35 list price vs. $21 at Amazon.) Mr. Stephenson's co-writer is Nicole Galland, and they make a mighty team.
Genre pigeon-holers will have a tough time. There's plenty of hard SF, time-travel implemented via ingenious gadgetry based on Schrödinger's famous box; but (oops) the gadgets only work with the cooperation of actual witches, which makes it kinda fantasy; and there's plenty of historical-fiction-style derring-do; and there's Tom Clancy-style military intrigue. And…
This is kind of neat: the primary protagonists, Melisande Stokes (newly-minted linguistics Ph.D. and Harvard instructor) and Tristan Lyons (DARPA guy) actually "meet cute". So, yes, there's kind of a strong romantic-comedy thread here too.
And also actual comedy. The whole book is pretty funny (you kind of have to ignore the wholesale slaughter at a suburban Boston Walmart, but…) and there are common outbreaks of hilarity.
And page 164 has a surprise I probably should have seen coming.
In short, highly recommended, especially for Stephenson fans and everyone else too.