Matt Haig’s award-winning books for adults and children include Reasons to Stay Alive and A Boy Called Christmas. Born in 1975 in Sheffield, he now lives in Brighton with his family. His new children’s book, Evie and the Animals, follows a girl with a secret superpower: she can understand and talk to animals.

Your Christmas trilogy was written in response to your son’s question “What was Father Christmas like as a boy?” Does Evie and the Animals have an evolution story?
So that my daughter didn’t end up talking to her therapist in 20 years’ time about not being the special one, I genuinely asked her what she wanted me to write about. And she said: “talking animals”. I had to come up with a story that wasn’t just replicating Doctor Dolittle, and I wanted to somehow bridge the world of domestic animals and wild animals. I was also feeling more ecologically minded, as many of us are.

It’s your first collaboration with acclaimed illustrator Emily Gravett. How did this come about?
Her book Wolves was always out on my daughter’s shelf. Thinking of someone who would be great illustrating animals, for me it was always Emily Gravett. I like her style – it’s not quite realistic but it’s very detailed in a beautiful way that doesn’t alienate kids. I worked very closely with Emily on the book.

Alongside the animal magic, staying true to yourself and navigating the pressures of life are at the heart of the book.
In all my work I tend to be drawn to people with a condition that for some reason they have to keep secret. I’ve done that with vampires, with aliens and I’ve done it in How to Stop Time with a 439-year-old man. With Evie, talking to animals is another condition that’s kind of invisible but it’s very intense. This book is definitely not directly about mental health, but probably that experience of having had depression and anxiety and looking “normal”, but having this other world going on inside. I wanted that to be subtle, for it to be first and foremost an exciting adventure story.

What impact do you think modern life has on today’s children?
Kids are so overloaded, they’ve got so much stress. I’m contacted by parents on social media or email, beside themselves, wanting advice, and the age seems to get younger year by year. I definitely think it’s a good time to be putting positive, empowering messages out there to counterbalance that. We watch out for our own kids, and that’s probably one reason we homeschool.

How do the processes of writing for adults and children differ?
One of the reasons I like writing children’s fiction is it gives me a break from writing my mental health-themed stuff. A lot of adult writers feel children’s fiction would be limiting; I find it the opposite. Children are the best readers because their imaginations are wide open. That age around 8 to 12, when they are between different versions of childhood, is when they are still willing to go with the daydream. You can throw everything at them.

To mark Mental Health Awareness Week, yours is one of 16 Instagram accounts followed by the Duke and Duchess of Sussex to promote positivity and wellbeing.
I got a text from Bryony Gordon saying “we’re being followed by Harry and Meghan!” We were the only two personal accounts, and it’s nice to be recognised in that official way. I haven’t sent any drunken DMs... Whatever your view of the royal family, people with such a high profile choosing mental health as a thing to talk about is great, and particularly that male figures are doing it.

You have a love-hate relationship with Twitter…
Mainly I hate it, but I’m slightly addicted to it. I take it all with a bit of a pinch of salt now. It’s such a lesson in perspective and how wrapped up we can get in our own issues. But at the start of my career in 2004, I hated the isolation, so what I do like is the fact you can have conversations with your readers.

Your book A Boy Called Christmas is currently being filmed.
It’s quite surreal. My first book was optioned by Brad Pitt, I was flown out to LA... nothing happened. I’ve had so many books optioned, so many near-things. I was being so pessimistic about this until principal photography started. It’s exciting, I’ve been to visit the set and my children are extras. They are going to be elf schoolchildren and have had their ears measured.

What’s the last great book you read?
A book that really shook me and changed my mind about things was The Uninhabitable Earth: A Story of the Future by David Wallace-Wells. It’s about climate change and I think it’s going to be this generation’s No Logo. It’s powerful, motivating and scary as hell. A call to arms.

What books are on your bedside table?
I have a towering pile. I’m such an unfaithful reader. I’m a dipper and an abandoner. I’m reading Robert Hughes’s art book Barcelona, because I went there recently. Rhik Samadder’s memoir I Never Said I Loved You is raw and funny and about mental health. And Artemis Fowl by Eoin Colfer, which I’m reading aloud to the kids.

Which book did you expect to like and didn’t?
Most. I’m extremely critical, but I should say that I’m also extremely critical about my own books. You want something to absolutely shake you to the core. We haven’t exactly got a shortage of books, but we do have a shortage of time.

What kind of reader were you as a child?
I was massively into books at a very young age. Noddy Goes to Market by Enid Blyton I was obsessed by. The first book that felt like it wasn’t given to me by a parent or a teacher was The Outsiders by SE Hinton. That was the first book where I really understood that books could be as rebellious and entertaining as cinema and music, and not these wholegrain things you have to consume to be healthy and good.

Matt Haig will be speaking at Hay festival on 1 and 2 June (hayfestival.com).

• Evie and the Animals by Matt Haig, illustrated by Emily Gravett, is published by Canongate (£12.99). To preorder a copy go to guardianbookshop.com or call 0330 333 6846. Free UK p&p over £15, online orders only. Phone orders min p&p of £1.99