The hero of Frank Cottrell Boyce’s new book is Liam, who at age 12 has reached adult height and, as a result, is able to pass himself off as a chaperone for the ultimate field trip—a rocket ride into space. From his home in Liverpool, Boyce spoke to Bookshelf about Cosmic (HarperCollins/Walden Pond), which has already received three starred reviews.

What inspired you to write this insanely funny and wonderful book?

Two things, really. People of my age, we all wanted to go to space. Fly to the moon? That was the dream. So I started with that. And then, my family went away for a year, and when we came back one of my son’s friends had had a growth spurt. He was barely recognizable. His mother said something that I actually put in the book. She said,That’s not a growth spurt. That’s a mutation.” That’s a real line! Isn’t that terrible? She really said that.

Horrible! But that was enough to plant the idea for a novel?

It stuck with me. There are these ridiculous expectations of kids who grow early. I guess it’s a blessing that I’m quite small.

You have a bunch of kids yourself. Do they give you plenty of opportunities to practice your “dadliness,” as Liam calls it?

We have seven—four boys and three girls. The oldest is 24 and the youngest, 6. [Boyce is married to Denise Cottrell Boyce, whom he met at Oxford.] Parenthood is hard. I don’t know how good I am at it. I want to be better. So I guess that’s just me thinking about the concept of “dadliness” and how I can improve.

Do your kids read your works-in-progress?

Oh, they do, and they’re very generous and supportive. Good critics. And I have to add, they read a draft of Cosmic and they all hated it. I had gotten the character completely wrong. I had Liam being closed off and that made him very hard to relate to. I think what was said to me by one of the kids was, ‘You’ve lost it, bud.’ They told me in no uncertain terms it wasn’t working.

This is your third novel, following Millions and Framed. Is it getting easier?

It’s not getting easier, no, but I think Cosmic’s my favorite so far, because it allowed me to finally fulfill my frustrated dreams about going to space. I mean, growing up, I think I assumed that one day everyone would go into space, that the day was coming. This is as close as I’m to get, it seems.

You came to writing novels after a very successful (and ongoing) career as a screenwriter, including the screenplay for Millions. Any plans to turn Framed or Cosmic into films?

Framed actually has been made into a television film by the BBC. It aired here last year and there has been some talk about a release in the U.S. Cosmic, nothing yet.

Millions was a very unusual project since I believe you wrote the screenplay before you wrote the book, correct?

I did, and it took a long time to get the money together for the film because there was a child as the main character. So while we were waiting, Danny [Boyle, the director] said, ‘Why don’t you go ahead and write it as a book, too?’ It was a very easy book to write so I thought, stupidly, writing books was easy.

You didn’t feel constricted when writing the book by having already imagined it as a film?

It’s even odder than you think. I got a proof copy of the book on the day we finished filming and I gave it to Danny. He read it immediately and I had added things to the book that were not in the screenplay and he liked those things so we wound up reshooting parts of the film to put those things in. The most convoluted process possible, really.

Which do you prefer writing—the screenplays or the novels?

Probably the books.

Because you have more control over the finished product?

There are things that are very satisfying about film. Yes, there is the control issue but if you turn that around, the truth is you get a lot of feedback when you’re working on a film. That’s a different kind of control. But people possess books in the way they never do film. You live with a book for weeks and books soak up the circumstances in which you read them. You remember you read it on the beach, or on the train. You own a book in the way you never own a film. Since I’ve written the books, I’ve been visiting a lot of schools and I realize it’s a huge responsibility writing for this age group. That’s part of the thrill of it.

I bet the kids really respond to the humor in your books. Where does your wit come from?

I don’t know. I guess I want them to laugh. It’s important to me. There are a lot of people telling kids life isn’t worth living. I want to tell them it’s great.

Were you always funny? Were you the class clown?

I guess I was, which, now for me, when I’m at these schools, [the class clown] is a really annoying character.

You are not old enough [Boyce is 48] to have personally witnessed the Beatles’ rise to fame but you live in Liverpool—is their specter still a huge presence there?

I was more of the punk rock era but where I live now is one mile from where I was born and you can’t live in this town and not feel you’re under their shadow all the time. It’d be like growing up in Memphis and not knowing who Elvis Presley was. I grew up hating them but I’ve come round.

What writing project is on your screen now?

I’m about halfway through the next book. My heart is in writing the children’s books. That’s where I’m comfortable.

Cosmic by Frank Cottrell Boyce. HarperCollins/Walden Pond, $16.99

ISBN 978-0-06-183683-1