It's a couple of hundred years in the future, and it looks like the grumbling technophobes were right all along—the machines have taken over. More precisely, an apparently benign Artificial Intelligence collective called the Environment Agency, possibly run by a super-powerful AI known as the Watcher, has staged a bloodless coup over the anachronistic commercial ruling powers of our near future . . . an event referred to as the Transition. No one's complaining much; guided to a greater or lesser extent by this near-omnipotent government, humanity now exists pretty much in harmony.

The definition of what qualifies as human, it needs to be mentioned, has expanded a little. In addition to the flesh-and-blood models with which we are already familiar, the term "human" now encompasses Personality Constructs—computer-generated but fully sentient "copies" of biological humans. PCs live in the Digital world, an artificial realm or "Processing Space" that replicates the real, or "Atomic," world. The two realms are separate, but coexist on equal terms in communication and partnership. And then we have AIs, intelligences with no human template, some of which occupy robot bodies in the Atomic world, others of which remain as pure, unfettered mind in the Digital realm. They seem to be our friends, although the relationship is certainly not one of equals. AIs are built by other AIs, and as such have evolved exponentially, operating on a level of sophistication beyond human comprehension; their ability to influence the thoughts of both Digital and Atomic humans is a fact of which humans are aware and that AIs make no pretence of concealing. As personalities, they fall somewhere between Isaac Asimov's (and Robert Silverberg's) Renaissance robot, the Bicentennial Man, and Greg Bear's sentient but function-driven AI, Jill (for further information on her, consult Bear's Queen of Angels and its sequel, Slant, if you‘ve been unlucky enough to miss them). Intelligence is as much defined by the capacity for emotion as by capability, and AIs like Judy's robot friend Frances are, rather endearingly, as interested in pleasure as in purpose:

"You're a robot, Frances. You get off by someone entering Mersenne primes on your push buttons."

?Frances looked down at the little array of buttons that twinkled obscenely between her legs, then slowly raised her head to gaze back at Judy.?

"You know the combination, Judy," she said in a low voice. "You're more than welcome to try it." (p. 114)

So is this a crime-free world? Not always, hence the need for Social Care operatives like Judy. Along with her eleven "sisters," PC Judys who work in the Digital world, the Atomic Judy is a sort of cross between a social worker and a policewoman, tracking down whatever criminals manage to evade the constant, apparently benign observation of the EA. Judy and her Digital counterparts have been trying for years to close down the sinister Private Network, a torture playground where numerous illegally replicated versions of a single woman, Helen, are subjected to the tender mercies of the Network's twisted clients. Helen is rescued—at least, one version of her is—and joins forces with Digital Judy 3. United, Helen and the Judys learn of a counsellor named Justinian who, seventeen years earlier, visited a planet at the edge of another galaxy to discover why every AI that landed on that planet shut itself down. What they learn of his mission threatens to kick the legs out from under this stable society.

Yes, this is complex stuff that requires and deserves attentive reading from the outset, but don't worry: Ballantyne does an excellent job of outlining his future society and introducing his characters without ever oversaturating the reader, managing to succinctly convey the essentials early on without letting his text feel rushed or contrived (the chilling opening chapter grabs you like a Venus flytrap, introducing us to various replicated Helens who haven't yet discovered that they are prisoners inside the Private Network . . .). In a narrative structure as finely tuned as this, every event, revelation, or piece of dialogue works in harmony with the rest: a textual mechanism without a single loose cog. Take the two main narrative threads, which dance elegantly around each other with perfect timing; what the Judys discover flavours the next chapter on Justinian, whose own discoveries in turn lend dramatic weight to the Judys' investigation. The EA's records claim Justinian died peacefully on Earth; is Judy 11's anonymous informer telling the truth when he claims the Watcher altered those records? Either way, we come to the next Justinian chapter with tensions nicely raised.

A techno-thriller that aspires to be more than just detective fiction with gadgetry, Capacity successfully tackles themes like free will, accountability, and the nature of human consciousness. Humans have taken a back seat, but is that necessarily a bad thing? In Aldous Huxley's Brave New World, the ugly nature of the "conditioning" process and the ruling party's use of soma made it easier to side against that methodology, to champion the notion of something sacred and inviolable in humanity's right to decide for itself. Ballantyne, adept at placing the reader in a philosophical quandary, never gives us the luxury of making such an easy ruling; here the issue is a thornier one. The character of the ruling AIs remains tantalisingly ambiguous. The EA itself is a trapezohedron whose appearance constantly changes as its numerous facets catch the shifting light cast by Ballantyne's intricately interwoven plot strands. Does the EA gently guide humanity, or does it make our decisions for us? If the latter, where does that leave humanity?

It's to Ballantyne's credit that these weighty issues never threaten to occlude the individual characters, or to overshadow the sometimes painful attachment you feel for them. Justinian's discovery of the extent to which his self-determination has been eroded by the sophistication of the AIs is made all the more significant because you care about Justinian himself; character and theme complement each other, never competing or scrapping for page space. The closest thing to a flaw you'll find here is that, just occasionally, the characters verge on becoming mere voice boxes for articulating the novel's more elaborate speculations, causing the usually authentic-sounding dialogue to lose some of its believability. The only other niggle worth noting is the above-mentioned complexity, and that's really in the hands of the reader. Take your eyes off the plot for a minute and it'll slip from your grasp like an eel, necessitating annoying back-pedalling through the pages, but take the phone off the hook, switch off the TV, and you'll be fine.

Some happy news: a second course is on the way, and an earlier novel in the series, Recursion, is already on the shelves. Capacity's sequel Divergence is definitely on my shopping list, and all three books should be on yours.

Finn Dempster lives in Bristol, England, and can usually be found in his local library, pub, or bookshop. He holds an English degree, and is dithering over the notion of doing a PhD. He reviews books and film for ezines and his local press.