It is a strange quirk of memory that some books I read decades ago are still clear in my mind, while others read more recently I have forgotten entirely and ring no bells even on re-reading. This is not necessarily to do with the quality of the writing as the latter group include some good stories; it seems to be a matter of the strength or clarity of the images created in my mind. Psion is in that latter category but is none the worse for that, so I was able to enjoy re-reading it as if for the first time.
This is one of several popular SF novels written by Joan D. Vinge in the early 1980s, often with something of the feel of fantasy. 'Psion' is set in a distant future when humanity has spread to many star systems by means of FTL spaceships and has encountered another sentient race, the Hydrans, who are close enough to humanity to interbreed, thereby indicating a common origin. The Hydrans possess a formidable range of psionic powers, including telepathy, telekinesis, teleportation and precognition, but they are psychologically incapable of violence or deceit, so are soon dominated by humanity. Some humans have also developed psi powers, but usually only one and to a limited degree. They are regarded with fear and suspicion by the rest of humanity.
'Psion' is a first-person account of a teenage human-Hydran hybrid, called Cat because of his Hydran vertically-slitted eye pupils. He grows up an orphaned, illiterate and feral sneak-thief, living in the gutter and with no memory of his origins. Eventually caught, he tests positive for psionic potential and is taken to a research institute which aims to develop his latent telepathic ability. While there, he meets two other psions, Jule and Siebeling, and learns that they are part of a plot to trap an elusive human super-psion criminal dubbed Quicksilver. What follows is an exciting adventure thriller mainly set on the strange world of Cinder, still occupied by Hydrans, in a battle for control of the only source of the Telhassium crystals required for space flight.
This is more than just a simple thriller, as there is a strong focus on Cat's sufferings as he tries to develop his ability and understand where he came from, plus learn the dark secret buried so deep in his mind that not even the most powerful telepath can reach it. His relationships with Jule and Siebeling are complex and form the main sub-plot. The conclusion is unexpected but convincing.
First-person accounts are not so popular these days because of the restricted perspective they involve, but this worked for me. I enjoyed the story and found myself keen to get back to it again after each break. There is a sequel, Catspaw, which I hope to get around to re-reading soon.