I've not had much time this week. I did finish this on the last day of February.
It was an odd reading experience - I don't know if it says something about my state of mind then (stressed somewhat) but I read it quickly - it's undoubtedly smoothly written - even though I'm sure I didn't take in all of the scientific arguments. And scientific arguments are all this book has, the alien encounter storyline being a peg to hang all of this on. (In this is reminded me a little of Rendezvous with Rama.)
It's the hardest hard SF I've read in a long while, and a little too hard for me. The back cover quotes the Washington Post which talks about Watts's "richly developed characters". They clearly have a different definition of characterisation than me. I can read hard SF - though personally prefer someone like Ian McDonald, who has a more distinctive prose style and can do characterisation as well. Talking of whom, I have his The Dervish House in the pile...
And talking of Watts, I should be reading his short story "The Things" soon, as it's on the BSFA shortlist.