Three-time Caldecott Medalist David Wiesner gave a preview of his latest picture book, Mr. Wuffles! (fall 2013), at Houghton Mifflin Harcourt’s Boston offices to staff and a few media friends earlier this week. After praising his creativity and the meticulous care he puts into his books, Wiesner’s longtime editor, Clarion publisher Dinah Stevenson, noted that his work is “always surprising. I would never have predicted his next book would be Mr. Wuffles! – ending in an exclamation mark.” Especially after Wiesner described the many twists and turns the story took over the course of many years. It began as Hail the Conquerors and soon became Greetings, and was interrupted by the publication of other picture books, including The Three Pigs (2002) and Flotsam (2007).

“It goes against the grain to show it so early,” said Betsy Groban, senior v-p and publisher of the HMH Children’s Book Group, who called the book “a masterpiece.” The story about tiny aliens crash-landing on Earth, only to be threatened by a cat – the Mr. Wuffles of the title, who thinks their space ship is a toy – has been written, but Wiesner still has a third of the artwork to complete. He showed finished art for scenes depicting the cat, the aliens, and the helpful bug community living behind the wall.

Wiesner spent many years off and on refining the story, which was inspired by a cover he created for Cricket magazine back in May 1993. That’s not the first time a cover led to one of his picture books; Tuesday also started as a Cricket cover. As for the cat, which was a late addition to the story, it’s modeled on his own black-and-white cat. Wiesner, who is using watercolors for the illustrations, had never painted a figure in black before. To get the depth of color required for Mr. Wuffles, Wiesner painted 12 to 15 layers of black on top of a base color.

After Mr. Wuffles! is finished, Wiesner told PW, he has several more projects in mind, among them another picture book and his first graphic novel, something he’s long wanted to try. But if he’s learned one thing from the two decades it will have taken him to complete his newest picture book, he said, “[it’s] persistence. Never give up on an idea.”

Mr. Wuffles! by David Wiesner. Clarion, $14.99 Oct. 2013 ISBN 978-0-618-75661-2