Children across Britain have chosen a magical adventure about a boy taught by pirates on a school ship as one of the best books of the year, it was announced yesterday.

Fergus Crane, by writer Paul Stewart and illustrator Chris Riddell, won the gold medal for books for children aged six to eight in the Nestlé Smarties book prize, and the award given by the charity 4Children.

"This richly woven novel is highly illustrated, which adds another dimension to the book and increases its appeal to this age group," said Julia Eccleshare, who chaired the panel of adult judges.

Sally Grindley's Spilled Water, a harrowing tale of child slavery in 20th century China, won gold in the nine-to-11 age group and Biscuit Bear, Mini Grey's story of a biscuit's adventures, won the top prize in the under-fives category.

The winners were announced at the British Library in London. Ms Eccleshare said: "This award counts because the final choice of winners is made by children, who are the toughest critics of all. This year's young judges chose the winners from an exceptionally strong and varied shortlist."

Adults select the Smarties shortlist but children decide who wins.