Michael Morpurgo's novel Shadow has won this year's Red House children's book award, which is voted for by young readers.
It is a third win for Morpurgo, who becomes the only author to do so in the award's 31-year history.
Shadow tells the story of boy who is befriended by an army sniffer dog in Afghanistan.
"Shadow was a difficult book to write because I was writing about a contemporary conflict," Murpurgo said.
He was presented with the award at a ceremony in Birmingham on Saturday.
His book, which is partly set at a detention centre for asylum seekers in the UK, was published last September.
'Raw and real'
"I was conscious of the fact that there are families of soldiers who are fighting now in the war and dying in it," said the 67-year-old author, who is based in Devon.
"So there is a sensitivity that is raw and real. I wrote Shadow, as I do with all my books, because I felt so passionately about the subject - the detention centres and the suffering of war.
"I felt compelled to write it but wasn't sure how it would be received. Winning this award, voted for by so many readers, means such a lot."
Shadow won both the category for younger readers and the overall prize in the awards, which is co-ordinated by the Federation of Children's Book Groups.
Morpurgo's previous wins were for Kensuke's Kingdom and Private Peaceful.
His novel War Horse, published in 1982, has been made into a successful theatre production in the West End and on Broadway.
A film version, directed by Steven Spielberg, is out early next year.
Other winners at the 2011 book awards were Angela McAllister and Alison Edgson's Yuck! That's not a Monster in the category for younger children, and Alex Scarrow's TimeRiders in the older readers' category.
Previous winners of the award include JK Rowling, Robert Swindells, Roald Dahl, Jacqueline Wilson, Malorie Blackman and Sophie McKenzie.