Less than a week to save the world ... will they succeed?

The sci-fi novel in which creatures from another planet visiting Earth is not very popular at the moment in the world of youth fiction best-sellers. Vampires and werewolves have overtaken aliens.

But it's more than possible, that with Philip Webb's Six Days, the extra-terrestrial will be making a welcome reappearance on the pages of teen novels.

Webb's debut is imaginative and great fun to read, with a seamless mix of genres. Teenager Cass and her young brother Wilbur, helped by two teenage humanoids from somewhere out in deep space, have six days to save Earth from being obliterated. Their mission is all set against the backdrop of a dystopian London that has been ruined by biological warfare.

A century ago, London was attacked by Russian armies: the buildings were left standing, but most of the humans were wiped out. The few people still living in the city are forced to work as scavengers, or "scavs", and search the ruins to find what they can to survive.

The enemy Russians, known as Vlads, have been running what was left of London, and they have taken it upon themselves to organise the gangs of scavs into units. These units have one main goal: to find a powerful, mysterious object called "the artefact".

No one knows what "the artefact" looks like, what it does or why the Vlads want it. But it must be found, and Cass and Wilbur are among the many people who have a lifelong job of pulling London to pieces and tossing the remains into crusher chutes.

Webb thrusts his reader right into the middle of the adventure. The scene is set quickly and we meet the engaging central character right away. When Cass' little brother vanishes, she goes to find him before the Vlads can. She discovers Wilbur hanging off of the minute hand of the most famous clock in the world, Big Ben. With the help of a strange looking boy called Peyto, Wilbur is rescued.

Cass soon finds out that Peyto has dropped into London from a spaceship. He is here on a mission, and Cass and Wilbur become caught up in a race against time to stop the total destruction of Earth. The opening pages of Six Days are thrilling, and Webb keeps up the momentum throughout, with a plot full of brilliant invention.

Webb uses Cass as the narrator of Six Days, and her familiar and simple tone takes a bit of getting used to at first. But Cass is such an appealing character that the reader is easily pulled along by her personality, concerns and adventures.

Webb is a terrific storyteller, and he fully involves his readers in this entertaining novel. There are occasions when bits of the plot don't quite add up, but this doesn't really matter. Six Days is a lively read, so just go along for the ride and enjoy.

John Millen can be contacted on [email protected]