This girl's life, for children and adults

Fiction: How I Live Now is American-born Meg Rosoff's startlingly good début novel, and on the strength of this one book alone, Rosoff has achieved that rare thing: she has instantly established herself as an extremely fine writer.

When this manuscript was originally auctioned in a bidding war, it was bought by Puffin to be marketed as a children's book, but the novel has now been brought out within that publishing company as a Penguin hardback. This is a clear indication by the publisher that it correctly sees How I Live Now as belonging to that extremely lucrative new category, the crossover book, appealing to both children and adults, as with Philip Pullman's bestselling trilogy, His Dark Materials.

How I Live Now is 15-year-old Daisy's story, set in modern rural England, where her new home is a huge ramshackle house deep in an unnamed county. American Daisy comes from New York to stay with her four English cousins while her father and stepmother - with whom she is on very frosty terms - prepare for the birth of their new baby. Daisy is a full and memorable character from almost the first page: independent, spiky, vulnerable, honest and laconic. She also has an eating disorder, which is never named, but is clearly something very close to anorexia.

The book opens with Daisy's arrival at an airport in England. She is collected - and driven home - by her immediately intriguing 14-year-old cousin, Edmond, who sports a cigarette and hair "that looks like he cut it himself with a hatchet at dead of night". Her Aunt Penn does not show at the airport, because she's working. It emerges very early on that Aunt Penn "always has Important Work To Do Related To The Peace Process".

A war of terrorism lurks first in the background of the book, then gradually comes more and more both to the forefront of the action and of Daisy's consciousness. Daisy is vague about details and politics, and we hear about the war only in the ways that it affects herself and her cousins, while we as readers also gather enough information to see the bigger, quite terrible picture of a country at war with an unidentified enemy: "A bomb went off in the middle of a big train station in London the day after Aunt P went to Oslo and something like seven or 70,000 people got killed."

All the airports close, and Daisy is stuck in England, with only her young cousins as family.

How I Live Now is a compelling story of survival, of very real modern fears, of war, of an extraordinary family - and of love. Daisy and Edmond discover very uncousinly feelings for each other, and "Things Happened in spades".

There are things in this book that, in theory, shouldn't work, such as the absurd names of Daisy's cousins: Osbert, Edmond, Isaac and Piper (a girl). Surely it's risky to give such fey names when you're writing about such solid realities as terrorism. And risky also to establish characters who then simply drift out of the action, such as Leah, Jane McEvoy and Alby. Not to mention the anorexia and the complex and delicate love element. Yet everything works. This is a beautifully written, marvellously original book, where the prose is so arresting and thought-provoking you find yourself rereading entire paragraphs, and then putting the book down and thinking about the bit you've just read. Yes, How I Live Now really is that good.

• Rosita Boland is a poet and an Irish Times journalist