Bestselling picture book creators Mac Barnett and Jon Klassen will kick off a new series in 2017, Candlewick announced jointly with Walker Books Group. The first book, Triangle, will release simultaneously worldwide on March 27.

“I feel like in the glacial world of children’s publishing announcing that a book is less than a year away is like our version of a Beyoncé drop,” Barnett told PW. Square and Circle will follow in 2018 and 2019, respectively.

Despite the titles, these are not concept books but a series about friendship along the lines of Frog and Toad, the classic Arnold Lobel tales, Barnett said. In the debut, Triangle plays a trick on his friend, Square. Maybe. It could be that Square has pulled a fast one on Triangle. “The book is all about sneaky tricks,” Barnett said.

The idea began with drawings Klassen had been working on for many years. “It was an older visual concept that came from a period when I had more time to do one-offs, with characters I made from shapes,” Klassen said. “All the shapes have the same size eyes but with the triangle, you have to set the eyes way down in his body and, for some reason, that made him look shifty. That was so interesting, that just from where you placed his eyes implied something about his character. All of sudden he became a trickster, whereas Square is just more solid and conservative because, well, because he’s square.”

“Square is a square dude,” Barnett added. “He’s got a routine and isn’t as sharp as Triangle.”

Klassen had characters but no story when he showed the drawings to Barnett, with whom he had already collaborated on two Caldecott Honor books, Extra Yarn (Balzer + Bray, 2012) and Sam and Dave Dig a Hole (Candlewick, 2014). “We talked about it until we came up with the introduction because we had to set the stage – introduce the tone of the story – before it could begin,” Klassen said. “But once we got that done, Mac said, ‘I can take it from here,’ and he went back and wrote this really hilarious text. I would have gone really concept-y but Mac’s so loose that what he came up with was this really funny story about these two pals.”

Barnett and Klassen met in 2008, at a party that their now mutual agent Steven Malk holds each year to coincide with the annual SCBWI conference in Los Angeles. Neither of them had been published yet. “Steve introduced us and we started talking about books we loved as kids and both of us had a deep love for Frog and Toad,” Barnett said. “Jon and I still talk about Frog and Toad all the time because those books are as good as anything written in English and show how multifaceted relationships can be. Every story takes a different approach to tell you a little bit more about what these two guys mean to each other.”

Aesthetically, the book design is “somewhere between a board book and a picture book,” Klassen says. “I wanted a board cover and the pages cut flush to the cover because they should look somewhat geometric, given the theme,” he said. The interiors are in full color.

Although only the first book is written, Barnett said he and Klassen have a ton of material they haven’t shaped yet. “We have a lot of stories about these characters so there’s no panic about generating more. I think Jon and I would both be delighted if this trilogy were just the beginning.”

Triangle by Mac Barnett and Jon Klassen. Candlewick, Mar. 2017 $18.99 978-0-7636-9603-0