I was excited as I read the first half of Capacity. Ballantyne sets up an interesting, if not entirely original, future world. Seemingly benevolent AI's watch over mankind, guided by a semi-mythical chief AI, "the Watcher," which may be extraterrestrial in origin. Copies of human personalities live in processing spaces that mimic the real "atomic" world. Harmony and peace are ensured by "Social Care," who tend to every need both physical and psychological. If problems arise, they are dealt with by agents such as Judy, the main character - or characters, since the "atomic" Judy has 12 copies that patrol the virtual world. The Judies are hunting a virtual predator, Kevin, who has been torturing multiple copies of a woman named Helen. Meanwhile, halfway to the Andromeda galaxy, the AI's have encountered an alien threat that seems to feed off intelligence in any form. And it is heading our way. A promising set up. . .
By the end of the book, I was less satisfied. I understood the world as the backstory filled in, but the storyline remained enigmatic. Worse, the motives of the characters are too obscure for their actions to fully make sense. After spending 300 pages with Judy, I still don't get her. By the end of the book, I'm not sure who is on whose side, what they are trying to accomplish, and why. I don't need protagonists in white hats and villains in black, but if I'm to care, things need to be better defined than this.
Also, though the world is fairly well explained, it is not fleshed out. Ballantyne has about 10 characters in the book, which is enough, but they almost never interact with anyone else. We never see another agent, or Judy's boss, or neighbors, or passersby. There is not enough detail to bring the everyday world to life.
All in all, Capacity was worth reading. I imagine much will be cleared up in the sequel, so that it all makes sense. But I'm not sure I care enough to find out.