I've been pondering this one for a few days. It's well done, as were the others in the series. However, I felt like it got more into science theory than the others, which is fine, but not my favorite. It was relevant to the actual interesting bits (to me) of the story, which is at least good, imo.
So, the story progressed in some interesting and unexpected ways, which is always cool. I liked the way Yi progressed from paranoid/unstable genius to paranoid/stable-ish/sneaky genius. I thought she had a great arc.
I did spend the last third of the book expecting a particular reveal to take place, BUT IT NEVER DID! The ending was a lovely uncertain thing, rather like the ending of La Femme Nikita (French movie) rather than the usual all wrapped up type ending of Point of No Return (American remake).
I felt the series overall was …