Once again, as in Stardance, Robinson has returned to the scene of the crime and fleshed out a short story to create a full length novel. To be quite honest with you all, I don't think Robinson really has "the chops" to write a full length novel from scratch - each of his novels ends up being a loosely connected collection of episodic short stories, to some extent. Not that he's not enormously entertaining and talented at those, but the long form is not his strength.
There are two main threads to the story; two protagonists. The first, whom we met in the short story, Mindkiller, is Joe the burglar. Joe is pretty much the ghost in the machine. He has no past, no official existence, and no recollection of who he is or how he ended up in residence in a luxurious hidden bunker with state of the art computer systems, tailor made, it seems, for someone like him to fly under the radar, supporting himself by burgling the wealthy. Joe makes a decision to meddle in some one's life when he rescues Karen, a hooker, from slow suicide by "wireheading". Wireheads are folks who have had a device surgically implanted in their brains which directly stimulates the pleasure center. Such stimulus is highly addictive, and wireheads will go without eating, drinking, sleeping, or even moving as long as the current keeps flowing.
The other protagonist is Norman Kent, a mild-mannered, somewhat hapless professor of literature in Nova Scotia. His wife has left him for a young plumber, his career is stalled out, and we meet him when he is standing on a bridge, ready to kill himself with a plunge to the icy waters below. The incongruous desire to save his hat, when it is blown off his head, results in aborting his suicide, and he returns to his apartment to find his long-lost sister, Madeleine, awaiting him there after her long sojourn in Europe. There's some sorrow buried in Maddie's past, too, which she won't reveal, but she stays with Norman for a while, helping him get his head back together, until she is abducted without a trace while walking home from a party late at night. Norman's search for his sister is fruitless, and he eventually appears to give up hope of finding out what happens to her, and begins to get serious about his teaching career again.
The "link" between the two men appears to be two technologies that are also linked: the ability to directly stimulate the pleasure center of the brain, and the technology to allow memories to be deleted or edited from the brain, which turn out, through the course of both men's investigations, to be owned and controlled by a single entity, whom Robinson calls, later in the book, The Mindkiller. Both men indulge in quixotic quests to surprise and neutralize the villain, and the results provide some twisty plot fun in this novel.
In the end, however, it boils down to Robinson's favorite idea; that if only mankind could get into each other's head in some way - usually telepathically, but in this case by recording one person's memories and imprinting them upon others, war, poverty, hunger and all evil will disappear from the world. A good example would be to imprint the memories of a modern farmer, with everything he knows about proper planting, fertilization and irrigation techniques, into the mind of a peasant farmer in the third world, or if a KKK member could experience exactly what it's like to be a persecuted minority.
Great concept, and obviously the technology is too dangerous to turn over to any particular country or government, lest it be abused, hence the conspiracy to keep the knowledge tightly held until it is fully developed and can be revealed to the entire world, free to all. I still see some logistical problems, but perhaps it could do some good - minor shades of this in real world things like the OLPC project, and efforts to bring "micro" water treatment facilities to third world countries, and with vertical farming, etc.
One thing I found amusing was a paragraph in the last chapter:
"...the man who pulls the President's strings, dear. For decades now, it has been impossible for a man suited to that power to be elected. Stevenson was the last to try. The rest of them accepted the inevitable and worked through electable figureheads. There hasn't been a president since Johnson who wasn't a ventriloquist's dummy. Some of them never knew it. The present incumbent, as a matter of fact, has no idea that his is owned and operated by a mathematician from Butler, Missouri."
There's just so much that's fun in that bit. The rest of the book is pretty fun, too.