The Arizona Kid. By Ron Koertge. Walker Books pound;5.99 pbk

Maximum Ride series: The Angel Experiment. By James Paterson. Headline Pounds 5.99 pbk

Nothing Scares Me. By Gene Kemp. Faber 5.99pbk

Half Moon Investigations. By Eoin Colfer. Puffin pound;12.99

Sex, violence, swearing? Or just a great thriller? Fiona Lafferty sticks her own warning label on fiction for pre-teens and above

What makes a book a teenage book? A reading age of 12-plus means being able to read almost anything, so it must be subject matter that dictates whether a book is suitable only for teenagers. The difficulty is that teenagers mature at different ages. The most publishers seem to do is put a warning in very small letters on the back of a book to the effect that “this book is unsuitable for younger readers”, which, frankly, could mean anything.

Adopting the age-rating that films and computer games have would give a better idea of the kind of content one might expect to find in a book. For example, PG books might include some violence, 12A books might have the odd swear word, and for those rated 15 expect stronger language and references to sex.

Using these ratings, Henry Tumour would be a 15. It is a deeply uncomfortable book and one that is difficult to describe. In bald terms it is about Hector, a teenage boy who has a brain tumour: a tumour with Tourette’s that starts to “speak” to him inside his head. This is disturbing on two levels. First, the tumour wants to survive, and inevitably this must be at the cost of Hector’s life. Second, “it” forces Hector to think in ways and about things he has never contemplated before, like sex and girls, which makes him uncomfortable. The book is completely compelling; it has an integrity that is impossible to ignore. I finished it wanting to recommend it. My only problem was, to whom?

The Arizona Kid is Judy Blume for boys and also a 15. It tells the story of the summer that 16-year-old Billy Kennedy spends with his uncle in Tucson, Arizona. Like many 16-year-old boys, he is obsessed by girls, but the other side of Billy is a serious young man, intent on becoming a vet, whose uncle has got him a summer job with a racehorse trainer. Here, he meets and falls in love with Cara Mae, a girl with whom he has his first sexual encounter.

The surprise element in the mix is that his uncle is gay and the way Billy comes to his own terms with this is sensitively portrayed.

James Paterson’s Maximum Ride series features mutants that are the result of bizarre experiments: winged children and creatures that “morph” from human into wolf form. A group of these flying children have escaped the “hospital” where they were created. Gradually they realise that they must be fitted with microchip devices as they are tracked down. High literature this is not, but it has the same appeal as a middling horror film. I would rate it 12A, but wouldn’t make the adult actually read it.

Nothing Scares Me, by contrast, is suitable for younger readers. A straightforward thriller, involving a girl who has premonitions of terrible events, it builds atmosphere well. When a pupil from her school goes missing, Petra repeatedly sees a vision of a girl with a dog in a lane, which she takes to be the missing girl. The twist at the end is a tad predictable, but pre-teens will enjoy it nonetheless.

We are now so used to Eoin Colfer’s easy style in the Artemis Fowl books that we might assume it is as effortless to write as it is to read. He has created another great character in Fletcher Moon. Fletcher is fixated by being a detective - he has a badge - and is called in to solve a series of thefts in a school. When he ends up in hospital, with a broken nose and under suspicion of arson, he has to go undercover to discover who is sabotaging his investigation. The dry, Irish humour mixed with a “Philip Marlowe” voice make this a delightful read and one that should definitely carry a U certificate.