Like most of Hamilton’s recent books JU is a fine example of bloat. Unlike most other books with excessive bloat it’s still a good read (at least partly). The main storyline about the war with the aliens from Dyson Alpha and the conspiracy of the Starflyer remains less interesting than the detailed setting Hamilton has created (something I already mentioned when talking about the first book).
The problem with the second book is that the plot is overly predictable (which wasn’t too much of a problem with the first part of the duology). That’s not so bad when the actual story segment you’re reading follows an interesting character (Paula Myo or Ozzie), but when not is becomes quite boring and wearisome.
The highly detailed nature of the book is both weakness and strength. Where other SF books only mention an interesting aspect of the setting in passing, Hamilton dedicates whole subplots to explore them. This makes his future feel very real. It’s easy to imagine how the Commonwealth grew out of our present, the impact the technologies Hamilton posed (wormholes, rejuvenations, mind backups) had in detail and how they shaped this specific future. Everyone who loves reading detailed future histories will get a kick out of the Commonwealth books.
Also the uneven distribution of wealth and technology allows for humans who don’t feel too different from present day humans to the more extreme end of the transhuman spectrum. All this makes Hamilton’s far future setting more approachable than the likes of Egan’s Diaspora or Stross’s Glasshouse.
I just wish Hamilton learned how to write something less bloated. Despite how much I enjoyed some aspects of the books, I can’t imagine ever rereading them.