Regenesis, by CJ Cherryh, 2009
This book picks up right where Cyteen left off, and it doesn't really give any refreshers. Ari II is coming into her own at Reseune, dealing with the politics and betrayals and interpersonal shenanigans left over.
Like Cyteen, this book considers the question "what would happen if we could engineer psychology along with genetics?" Like many other novels by Cherryh, there is also a lot of political intrigue, backstabbing, etc.
It wraps up many of the questions left in Cyteen, but I didn't find the ending as satisfying as I wanted it to be. There's very little denouement, but at nearly 600 pages, I'm not sure there's space for more.
If you enjoyed Cyteen and you want to know what happens to Ari II, you'll find out in Regenesis. I wouldn't recommend this to someone without any other familiarity with the Alliance-Union universe, however.