This novel is the source text for Ridley Scott's dystopian masterpiece Blade Runner, and it's to Philip K Dick's considerable credit that neither book nor film seem dated. Indeed, barely a year goes by without the arrival of some technological advance that makes the future dreamed up by Dick in 1968 seem closer. Hovercars may be a while off, but video calls and genetic modifications are firmly in the here and now. The very first pages introduce "mood-organs", dialled up to suppress or stimulate feelings among a needy population. It's difficult not to compare them to the internet: always on, always accessible, never quite real.

However, it's doing Dick a disservice to cast the novel as merely the prophetic outpourings of a writer obsessed with ideas. In fact, this is a thrillingly human work. The plot might ostensibly follow the attempts of bounty hunter Rick Deckard to track down and "retire" life-like androids who escaped from their human owners on Mars and have returned to an Earth ravaged by World War Terminus. But it isn't so much the fulfilment of this quest that matters, rather Dick's philosophical exploration of what being "alive" actually means.

The nightmarish chapter in the android police station, where Deckard's character is thrown into doubt, is pure Hitchcock – and as such it's a surprise it never made it into the film. But it only serves to show that Dick could be by turns a pulpy thriller writer, a hero figure to the science fiction crowd, and a novelist with a proper commitment to his characters. That this fantastic book bears scrutiny nearly 45 years on is proof that, with ...Electric Sheep, Philip K Dick was at the height of his powers.