An unpublished picture book by Maurice Sendak, author of Where the Wild Things Are, has been found hidden deep in his archives, five years after his death – somewhat like a little boy lost in the jungle after being sent to his room with no supper.

The typewritten manuscript and illustrations, co-authored by Sendak’s longtime collaborator Arthur Yorinks, were discovered in Connecticut by Lynn Caponera, president of the Maurice Sendak Foundation. Caponera was his housekeeper, assistant and friend for many years.

Titled Presto and Zesto in Limboland, the illustrations were created in 1990 to accompany a London Symphony Orchestra performance of Leoš Janáček’s Říkadla, a 1927 composition that set Czech nursery rhymes to music.

Caponera emailed the picture book to Sendak’s longtime editor, Michael di Capua, who told Publishers Weekly (PW) that he read it in disbelief: “What a miracle to find this buried treasure in the archives. To think something as good as this has been lying around there gathering dust.”

The new book will be published in autumn 2018, a posthumous release for an author regarded as one of the most influential picture-book creators of the last 50 years.

An illustration from Presto and Zesto in Limboland. Photograph: Maurice Sendak Foundation Inc

Presto and Zesto in Limboland was one of three collaborations between Sendak and Yorinks over a 15-year period – the other two were The Miami Giant, published in 1995, and Mommy? published in 2006.

Presto and Zesto in Limboland is an in-joke between the two, prompted by Yorinks’s move to Connecticut. “I only knew where Maurice lived in relation to the train station,” Yorinks told PW; Sendak thought they were half an hour apart. “Then I got in the car and I was there in three minutes. When he opened the door he said, ‘Presto!’ That became my nickname,” Yorinks recalled. Zesto was his nickname for Sendak.

The difficulty of translating the Czech nursery rhymes into English stalled plans to turn the original illustrations into a book. “It just seemed hopeless, like trying to translate Finnegans Wake, and Maurice had many other fish to fry,” Di Capua said. The illustrations re-emerged seven years later, when the violinist Midori used them for a fundraiser. It was then that the collaborators began working on a possible narrative for the 10 pictures. “The story became a homage to our own friendship so we named the characters after ourselves – Presto and Zesto,” said Yorinks, who also co-founded the Night Kitchen theatre with Sendak.

The project was then forgotten as Sendak began work with the playwright Tony Kushner on Brundibár, an adaptation of the Czech composer Hans Krása’s opera performed by the children imprisoned at Theresienstadt, the Nazi concentration camp. As the child of Polish-Jewish immigrants to the US, Sendak said his childhood was overshadowed by the deaths of relatives in the Holocaust.

On rediscovering the manuscript 20 years after he worked on it with his friend, Yorinks said: “The memory of writing it originally flooded back in a wonderful kind of way. We always had a lot of laughs for two really depressed guys.”