With the UK in the throes of a divisive election campaign and scientists warning that we are in a “planetary emergency”, Waterstones has chosen two titles that “call for a better and kinder world” as its books of the year.

After nominations from staff, a panel at the country’s largest book chain picked Charlie Mackesy’s illustrated call for love, friendship and kindness, The Boy, the Mole, the Fox and the Horse, as book of the year, and Greta Thunberg, author of No One Is Too Small to Make a Difference, as author of the year. Both choices, said bookseller Kate McHale, are “testament to the extraordinary power of books to move and shape us”.

The Boy, the Mole, the Fox and the Horse follows the titular characters as they explore the meaning of the important things in life. “What do you want to be when you grow up?” asks the mole. “Kind,” replies the boy. “What’s the bravest thing you’ve ever said?” asks the boy. “Help,” says the horse.

Mackesy’s publishers originally planned to print 10,000 copies but increased the print run to more than 200,000 within two weeks when it became a surprise Christmas hit.

Kurde, a bookseller at Waterstones Horsham, called it “beautiful in sentiment and look, the type of book you buy, then think who to give it to and end up keeping yourself”, while Nia at Waterstones Cardiff said that it “shows that love towards yourself and others is the only thing that truly matters in our hectic world”.

Greta Thunberg at the World Economic Forum annual meeting in January 2019. Photograph: Fabrice Coffrini/AFP via Getty Images

Thunberg’s collection of speeches was called a “rallying cry for the protection of our planet” and “one of the most influential books of 2019” by the chain. Bookseller Anna, from the Putney branch, said she didn’t think “there is a more important or powerful book than this one this year”, while Dave at Exeter felt it was “inspiring young people to change the world for the better”.

The shortlisted titles also included Candice Carty-Williams’s Costa-shortlisted debut novel Queenie, Margaret Atwood’s Booker-winning The Testaments, and Robert Macfarlane’s Underland. Waterstones said that nominations for both winners had been “singularly passionate, reflecting the strength of feeling towards two quite different books that have together defined 2019”.

“On the one hand we have the urgent message of No One Is Too Small to Make a Difference, from an author who has encapsulated and magnified the immense public concern over the climate crisis. On the other, the consoling beauty of The Boy, the Mole, the Fox and the Horse, an exquisite book that captures a yearning for a kinder world,” said the bookseller.