Mercy has a lot to be angry about: her mother is dead and the adults will not tell her what is going on. All her clothes look vile and her little sister can be a pain in the neck.
She might sound like a Jacqueline Wilson character, but Mercy is a Victorian girl (some of the time) who is going to live forever because her father has wrapped the family home in a spell.
Her story as told in journalist Sarah Singleton's first novel Century, published by Simon and Schuster, has echoes of Groundhog Day crossed with The Others, with more than a dash of Frankenstein-style gothic horror.
Century, which won the Booktrust Teenage Prize yesterday, is an intriguing story sifting through layers of time.
When it opens, Mercy and her sister Charity have lived for hundreds of years in an unending winter. They go to bed at sunrise and only leave the house for supervised walks in the dark: not supervised enough, because once Mercy discovers a woman frozen beneath the lake, she chases the truth like a terrier. The book deals with grief, loss, the pointlessness of stopping time and the power struggle between parents and children.
My fellow Teenage Prize judges and I chose the book during half- term from a shortlist of seven, grateful that we would not need to re-read it over Halloween.
Matt Whyman, the novelist, was one of its first supporters, back in the Easter holidays when we began to read 87 novels for 13 to 16-year-olds to choose a shortlist.
"It's perfectly formed, with the timeless feel of Frankenstein or Dracula,"
he said. "While it's a sophisticated and complex story, there is a strong human side. The language is accessible, and it contains what seems like a huge world in quite a short book."
Matt and I chose the shortlist with Terri Dwyer, the actress, Lucy Dalton, who teaches English at Kelmscott school in Waltham Forest, London, and Stuart Bryan, now in Year 9 at Reading grammar school. We were joined for the final stage by three young judges, Adam Cotton, from St George's college, Weybridge, Helen Comerford, of Wakeman school, Shrewsbury, and Maxine Stride, Somervale secondary, Radstock, Somerset, recruited through Booktrust's website www.bookheads.org.uk.
Geraldine Brennan is the literary editor of The TES