The Fractal Prince is the second novel by Hannu Rajaniemi and the sequel to his science fiction debut, The Quantum Thief. It continues the story of Jean le Flambeur, a daring adventure and thief in an advanced advanced far-future solar system. It is a direct sequel to that book, and I very strongly recommend reading its predecessor first.
The story focuses on the city of Sirr, the last surviving human settlement on Earth in a future where the planet has been ravaged by out-of-control nanomachines, called “wildcode,” and most of human civilization resides elsewhere in the solar system. Decades ago the Sobornost- a vast collective of uploaded human intelligences, or “gogols,” that is the dominant power in the solar system and seeks to eventually absorb all of humanity- was thwarted in its attempt to absorb Sirr when the wildcode rose up against them, forcing the Sobornost and Sirr into an uneasy truce. Much of Sirr's economy is based on the gogol trade, seeking out the buried still-operational computers running virtual reality afterlives that wealthy people of past eras uploaded themselves into and trading their occupants to the Sobornost.
Tawaddud, estranged daughter of one of Sirr's leading citizens, is given a chance to return to her family's good graces by serving first as a companion for Abu Nuwas, a prominent gogol merchant whose political influence is important to maintaining relations with the Sobornost and then as a guide for a Sobornost envoy. However, what starts as a mere social task soon becomes much more grave as internal unrest and violence begin to wrack the city, and tensions rise with the Sobornost- who would still gladly seize control of the city, its inhabitants ,and the entire planet if given the opportunity.
Meanwhile, legendary master thief Jean le Flambeur is still bound to the service of Mieli, a warrior from the Oort cloud who, for reasons of her own, is in the service of a Sobornost gogol with her own agenda. With her sentient spacecraft Perhonen, Mieli rescued Jean from captivity in a Sobornost virtual prison and heklped him recover some of his lost memories that his prior self had hidden away in storage on Mars. (See The Quantum Thief.) Now she and Jean must perform the task that Jean was broken out for: gaining access to the Kaminari Jewel, a data store with the key to unimaginably advanced technology vital to the ultimate goals of the Sobornost and it's godlike ruler, the Founder Matjek Chen. But the kaminari jewel is a product of the Zoku, a wide-ranging subculture of posthumans implacably hostile to the Sobornost, and won't reveal its contents to just anyone. The key Chen needs, whatever it is, turns out to be somewhere on Earth...
I enjoyed The Fractal Prince a great deal. The story is interesting and cleverly constructed (I won't specify how). I liked the characters, both those returning from The Quantum Thief and the new faces. It's also quite moving in parts- especially, rather surprisingly, the parts involving Matjek Chen.. There are some very exciting action sequences and elements reminiscent of heist movies, both of which take full advantage of the possibilities offered by the books ultra-advanced setting.
It's also very enjoyable and impressive from a purely stylistic standpoint. Rajaniemi's writing is filled with beautiful or clever moments without ever seeming self-conscious or eager to actively call attention to itself, and keeps events barreling along at high speed without ever seeming merely utilitarian.
Part of that is accomplished by throwing the reader into the deep end and expecting him to swim on his own, to an even greater degree than usual for far-fure science fiction. There are a lot of concepts and terms that the reader is left to figure out on his own, through context or previous knowledge. I think Rajaniemi does it very well, but if you don't enjoy that sort of complete-immersion worldbuilding you may find the book frustrating. For the same reason, it's also not a book or series I would recommend for someone who is relatively new to the science fiction genre.
The book further fleshes out the setting first seen in The Quantum Thief in some interesting ways. We learn more about Mieli's culture, a Finnish-influenced society settling the distant Oort Cloud, and see Earth for the first time. Sirr is a very interesting setting, like a fantasy out of the Arabian Nights recast in a post-apocalyptic, posthuman future where the grotesque remnants of past ages lurk in the desert and ruins like ghouls and those with the knowledge can bend reality around them to their will with mysterious "words of power" that command the omnipresent swarms of nanomachines. It's quite cool, and Rajaniemi does a good job of incorporating these fantasy-like elements without making Sirr seem less like science fiction- it still fits naturally into the rest of the ultra-high tech setting, rather than coming across like a fantasy world that's been transplanted into the far future with the word "magic" scratched out.
There's a great deal more about the Sobornost, a vast society of uploaded human minds, or gogols, dominated by "copyclans," uncountable minds originating as copies- or copies of copies, or copies of copies of copies, etc.- of just a few people, the Founders, branched off at different points in their progenitor's own vast lifetimes for different specialized purposes. It's a very interesting look at a radically different sort of society that is nevertheless comprised of individuals who are more or less psychologically human, some of the ways in which it functions, and the reason that the Sobornost uses human gogols for computing tasks that one might have expected to be the province of AIs or just mindless software.
We also learn more about the ideals and goals that drive the Sobornost, the “Great Common Task,"which are very human and yet suitably grandiose for rulers who exist in billions of simultaneous iterations and get their building materials by casually ripping globs of matter as massive as Earth out ofthe Sun.
One of my favorite bits is the Sobornost's abhorrence for the unpredictability of quantum mechanics. (This is just one of the implications of the Great Common Task, not its primary motivation or guiding principle,, but it's one that figures prominently.) For instance, there's a scene in which a higher-level Sobornost gogol speaks with some of his juniors who are running ultra-detailed virtual worlds inhabited by conscious simulations of people who lived in the pre-Sobornost era. A passing question as to whether the detail goes "down to the quantum level" leads to a panicked response from one of the researchers explaining the lengths they've gone to to avoid such "contamination." It's a brief thing, but the sense of paranoia and ideological intolerance it evokes is palpable.
That initially seems like a bizarrely esoteric thing to be angered by but, on reflection, makes perfect sense- dislike for the unpredictable or uncontrollable or messy is a common enough trait, one sometimes taken to an extreme. Take human beings with that sort of mentality and scale them up until they have the power of gods and intellects that fill computronium brains the size of moons, and the sorts of things flesh-and-blood humans try to impose order on pale into relative insignificance. It's the kind of moment I love in science fiction, where something that initially seems unreasonable, out of place, or downright absurd suddenly fits perfectly.
(I still remember, back when I was a little kid listening to Carl Sagan explaining what atoms were like in Episode 9 of Cosmos, being genuinely unsettled by the revelation that an atom's electron cloud contained almost all of the atom's volume but almost none of its mass, and that everything I thought of as solid was actually almost entirely empty space. So I can empathize with the idea of being offended by the behavior of subatomic particles more than most, perhaps. The chilling climax of this dramatic reenactment starring Agent Smith and Morpheus conveys it better than I ever could.)
Rajaniemi does interesting things with ideas like mind uploading and artificial intelligence, especially in the way he integrate some of them into the heist thriller elements of the book. Conflicts can leap from the virtual to the real and back as minds abandon their physical bodies or take them up again, move and copy themselves through computer systems and virtual reality environments, or transmit themselves as data from one physical substrate to another to stay a step ahead. People can radically alter their own personality and memories, take on temporary mental personae- in effect, actually be someone else- while their higher "metaself" oversees them, or go into states of altered consciousness appropriate to particular situations. Individual minds can be copied en masse, either entirely or in limited partial versions.
There's also a refreshing diversity of opinion on the philosophical ramifications of such copying. Some people are casually accepting of it, while others find the idea of being copied deeply violating. The Founders of the Sobornost have built an entire society around it and treat subordinate gogols-- including fully conscious copies of themselves- as casually disposable. Other issues are also raised-- for instance, the extent to which an earlier iteration of yourself who did things you can't remember doing was "you." The book doesn't focus on these things, but they are dealt with in an interesting way.
I strongly recommend The Fractal Prince and its predecessor, The Quantum Thief, for seasoned fans of science fiction, especially if you're interested in far-future settings or subjects like artificial intelligence, mind uploading, and posthumanism, or just like a fast-paced adventure story or crime/heist thrillers, provided you don't mind some fairly dense world-building. It's entertaining, finely written, has an intriguing and imaginative setting, and strongly rewards reading more than once.