Joseph Coelho has won the Yoto Carnegie medal for children’s books, marking the first time the prize has been awarded to a Black British writer. The current children’s laureate won the prize, which is judged solely by librarians, for his “beautifully descriptive” The Boy Lost in the Maze, illustrated by Kate Milner. The novel-in-verse is about a boy who, after learning the myth of Theseus at school, is inspired to search for his own long-lost father. It is “a novel that means a great deal to me,” Coelho said. “To have it recognised by the UK’s, if not the world’s, most prestigious award for children’s literature feels particularly special.” During his tenure as laureate, the author has joined a library in every local authority in the UK. “The one thing that has been consistent between all libraries has been the passion, skill and creativity of the librarians,” he said. “I feel completely honoured that it is librarians who have deemed The Boy Lost in the Maze as worthy of a Carnegie medal.” Aaron Becker was named winner of the Yoto Carnegie medal for illustration for his “beautifully crafted” and “universal” wordless picture book The Tree and the River Winning the prize is “an honour and a testament to the power of wordless books”, Becker said. “Within the pages of my wordless books, I invite readers to slow down and interpret stories on their own terms,” he added. “My hope is that winning this award promotes the idea that books can be for anyone, even the reluctant readers among us for whom story resonates more deeply through imagery than words.” The judging panel for both prizes was chaired by Maura Farrelly, a librarian at Victoria College Belfast. Both winners “are ambitious and exciting books that inspire the imagination and empower young readers”, Farrelly said. She described The Boy Lost in the Maze as “an extraordinary novel” that is a “multi-layered immersive read”, and the Tree and the River as “a beautiful visual narrative of the natural world and the impact of humankind which invites readers to become absorbed in the landscapes”. Both Coelho and Becker will receive £5,000 and a specially commissioned golden medal. Children from reading groups in schools and libraries also voted for their preferred winners, who will each receive a medal along with £500 worth of books to donate to a library of their choice. This year’s “shadowers’ choice” award for writing went to Tia Fisher for her debut novel about teenagers swept up into county lines, Crossing the Line. The Tree and the River scooped a double win, with Becker taking home the shadower’s choice for illustration as well as the main prize. The Carnegie medals were established in 1936 for writing and 1955 for illustration, open to books in the English language. Previous winners of the writing award include CS Lewis, Penelope Lively and Phillip Pullman; earlier illustration winners include Raymond Briggs, Shirley Hughes and Quentin Blake. Last year Manon Steffan Ros’s The Blue Book of Nebo became the first book in translation to win the writing prize, while Jeet Zdung won the illustration prize for Saving Sorya: Chang and the Sun Bear, by Vietnamese wildlife conservationist Trang Nguyen. Yoto, an audio platform for children, is the headline sponsor of the awards. The Boy Lost in the Maze by Joseph Coelho (Otter-Barry Books Ltd, £12.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply. The Tree and the River by Aaron Becker (Walker Books Ltd, £12.99). To support the Guardian and Observer, order your copy at guardianbookshop.com. Delivery charges may apply.