Harper Lee’s Go Set a Watchman and Paula Hawkins’ The Girl on the Train might have sold in eye-watering numbers over the last year, but booksellers at Waterstones have plumped for a sumptuously designed debut picture book about loss as their book of the year.

Coralie Bickford-Smith’s fable The Fox and the Star beat a shortlist that included Lee’s second novel and Hawkins’ thriller to be named book of the year by the UK’s largest bookselling chain. Managing director James Daunt called it “a book of great physical beauty and timeless quality, one that will surely join that very special group of classic tales that appeal equally to children and adults”. It won the bookseller’s top accolade ahead of contenders including Elena Ferrante’s much-praised My Brilliant Friend and Hanya Yanagihara’s Booker-shortlisted A Little Life “through the impassioned advocacy of our outstanding children’s booksellers,” added Daunt.

The title will now receive “the full and committed backing” of Waterstones throughout December. Last year, sales of Jessie Burton’s novel The Miniaturist increased by over 1,000% across Waterstones after it was named book of the year. Previous winners of the honour include Stoner by John Williams.

Bickford-Smith is a designer at Penguin Books, acclaimed for her work on Penguin Classics, but has “wanted to tell a story” herself since she was “very, very young”. Offered a book deal by Penguin’s Particular Books, she took a six-month sabbatical from a company where she has worked for 14 years to write and illustrate The Fox and the Star.

Inspired by William Blake’s poem Eternity – “He who binds to himself a joy / Does the winged life destroy; / But he who kisses the joy as it flies / Lives in eternity’s sun rise” – it tells of the forest-dwelling Fox, who loses, and mourns for, his friend Star.

“I had this idea buzzing at the back of my mind,” said Bickford-Smith. “And then, with the illustrations, I got to step away from my computer, and to draw and draw and draw, which as a child was all I ever did. Facing the blank page every day was really petrifying, and then things just happened.”

Facebook Twitter Pinterest ‘A book of great physical beauty’: illustrations from The Fox and the Star. Photograph: Coralie Bickford-Smith/Penguin

Waterstones said the picture book “has the classic feel of a fable and is a tale that speaks to all ages”, praising its “unparalleled, elegant design” and its “profound psychological understanding of loss”.

“I was thinking about how in life, if you hold on to something too tightly, you lose it, so to love something you have to let it go, and I wrote the story around that. It relates to so many situations – everyone has suffered – and it came together for me with losing my mum at an early age,” said Bickford-Smith. “Children seem to love the idea of the friends and the crazy illustrations, while adults like the concept of things being tough, but coming out the other side.”

Waterstones comes up with a shortlist after asking its booksellers to nominate a book “that stands out in its field and speaks to the company’s core customers – those people who love reading and love books”. The bookseller has said that it is set to announce its first annual profit in years, noting a surge in physical sales, as digital sales stall.

“I’m all about the physical book,” said Bickford-Smith. “We haven’t released The Fox and the Star as an ebook because I don’t think it would work – it’s all about the paper. I wanted to create something which harked back to the beautiful visual thinking of William Morris and William Blake, so that people would really appreciate the book as an object.”