It’s a story that gives the notion of collaboration unusual resonance. Chris Raschka collaborated with Vera B. Williams in a particularly heartwarming way on the late Williams’s final picture book, Home at Last. Relaying the story of a gay couple and their adoptive son adjusting to life together, the book is out from Greenwillow Books this month with a 75,000-copy first printing, just short of a year after Williams died of cancer. Two-time Caldecott Honor recipient Williams (A Chair for My Mother; More, More, More, Said the Baby) and two-time Caldecott Medalist Raschka (The Hello, Goodbye Window; A Ball for Daisy) shared a friendship and deep mutual respect, and though their collaboration was a rewarding project for Raschka, it was understandably bittersweet.

Williams, who penned the manuscript for Home at Last years ago but only recently decided to publish it, contacted Raschka (whom she had often encountered at PEN events over many years) in July 2015, after she realized that her illness might prevent her from completing the art for the book. She had earlier shared that concern with Greenwillow publisher Virginia Duncan, who has edited Williams’s books since 1997, initially alongside the imprint’s founder, Susan Hirschman, and then on her own after Hirschman’s retirement in 2003.

“Vera sensed, because she knew from her past experiences how much energy illustrating a book takes, that there was a chance she would not have the energy to finish Home at Last,” said Duncan, recalling a conversation with the author. “When she proposed the idea of asking someone to collaborate with her, we both went away from the conversation and came to the idea, independently, that Chris would be the ideal person for the project.”

Raschka was glad to hear from Williams, though was of course dismayed to learn the reason she needed help. “I had felt very close to Vera for years,” he said. “She had always taken such a sweet interest in what I was doing, and I loved her books, as well as her passion for justice and peace. I felt a certain connection with Vera, apart from artistically – but I think it is probably all connected. In fact I’m sure it is. I was more than happy to say ‘yes’ to the project – I could never have said ‘no.’ ”

Raschka visited Williams at her home in upstate New York for the first time in mid-August 2015 to look at her text and sketches for Home at Last. “I hesitantly took out some Post-It notes and started making small drawings as Vera spoke, to try to embody what she was saying about each spread,” he recalled. “After that, the thumbnails became storyboards that became larger, then a bit larger after that. She developed some drawings, and I did some, but the designs and the layout and the drawings of the figures were very much done by Vera’s hands.”

When he returned to Williams’s home to show her the first of his paintings for the book, Raschka admitted, he was a bit nervous – but unnecessarily, as it turned out. “She was more than happy with them, and joked about how nice it was to do a sketch and have me bring it back as a full painting – and that it was a nice little gig she had going there!” he said.

Though Williams never lived to see the final paintings for Home at Last, Raschka felt she was there in spirit as he completed them. “I really wanted to create something that Vera would be content with, and I did have her very much in my thoughts and consciousness,” he recalled. “Sometimes her voice was more distinct in my head than others, but, ultimately, she is very much there, on every page.”

Duncan observed that this is a fitting final work for Williams and not coincidentally. “I think Vera knew this was her last project, and I think it was a very important book to her,” she said. “Vera spent time in a children’s home when she was young, and Home at Last really illuminates so many themes she believed in, primarily that every child has the right to have a family and a safe place to be. I really feel so fortunate to have gotten to work with Vera at all – and especially on this book. It is something I’ll never forget, and I think everyone at Greenwillow feels the same way.”

As does Raschka, who added, “I feel as though this book was kind of a working and a living adventure. None of us knew quite how it would work out – in a way, we all went into it as explorers. I really believe this was a once-in-a-lifetime project for us all.”

Home at Last. Vera B. Williams, illus. by Chris Raschka. Greenwillow, $17.99 Sept. ISBN 978-0-06-134973-7