Author Michelle Paver has won this year's Guardian Children's Fiction Prize.
The African-born writer won for Ghost Hunter, the sixth and final book in her Chronicles of Ancient Darkness series.
Chair of the judges Julia Eccleshare hailed the series as a "towering achievement", adding Paver was a unanimous choice.
The author joins past winners including Ted Hughes, Jacqueline Wilson, Anne Fine and Philip Pullman.
Set in the Stone Age, Ghost Hunter tells the story of a boy, Torak, his female friend, Renn, and his lupine companion, Wolf, and their quest to defeat an evil group of mages, the Soul Eaters.
"It's relatively rare for a book late in a series to win a major prize," Eccleshare said.
"But the Chronicles of Ancient Darkness is such a towering achievement, as a whole as well as in terms of the individual books, that it was our unanimous choice."
Paver told the Guardian she had prepared her "loser's face" after being warned of the low success rate for long-running series.
But, she added, she was particularly pleased to win for Ghost Hunter because her aim was "to write six really good books and not have the thing tailing off".
The Children's Fiction Prize is unique in that it is judged by children's authors themselves, and no-one can win it more than once.
This year's panelists were Linda Buckley-Archer, Jenny Downham and last year's winner, Mal Peet.