Bright Young Things by Scarlett Thomas

'Bright Young Things wanted for Big Project.'
They're in the prime of their lives but our bright young things are all burnt out. Six sparky twenty-somethings just out of university and working dead-end jobs, they are all bored to tears with their lives and looking for a way out. When a mysterious job is advertised in the newspaper, they all apply.
What they least expect is to find themselves prisoners on a deserted island. There's food in the fridge and they have a bedroom each, but there's no telephone, no television, and no way to escape.