When island author and Newberry award-winner Karen Cushman sat down to write her 10th book for young readers, she knew only two things — the title of the book and that she wanted to do something different from her trademark historical fiction. Her efforts culminated in “Grayling’s Song,” Cushman’s first fantasy novel. The author will sign and read from her recently released book at 6 p.m. Thursday at Vashon Bookshop.

“I had the title, ‘Song of the Wise Woman’s Daughter,’ so I knew it was about a wise woman and her daughter but didn’t know anything else, so I started and typed the scene where the daughter discovers her mother rooted to the ground by a curse. Then I knew it had to be a fantasy,” Cushman said.

Like her two Newberry award-winning books, “Catherine, Called Birdy” and “The Midwife’s Apprentice,” her latest work is set in medieval England, an era she knows well.Cushman assumed it would be easy to write a fantasy — not worrying about facts, real people and places. But to her surprise, it became quite an endeavor.

“Not only do you have to have those kinds of boundaries (of people and places), you have to make them up, so there is an extra step involved,” Cushman said. “I had to make up the landscape and decide what magic was possible and what was not possible. You need boundaries and guidelines, so I really admire people who do heavy duty fantasy. They have a whole world to build. My world was pretty basically medieval with magic that mostly didn’t work.

Grayling, like all of Cushman’s characters, is well-drawn and faces a coming-of-age challenge that reveals hidden strengths and talents. Her task, along with her sometimes shape-shifting mouse named Pook, is to reverse an evil spell cast over all the magic makers — including her mother rooted to the ground and fast becoming a tree — in the kingdom. Sorcery plays a role in the story, but Cushman’s take on the nature of magic sends a different message than the typical fantasy.

“I purposely did not want a book in which magic solved the problem or saved the day,” she said. “I wanted the situation to be resolved through some help from Grayling’s companions but mostly from her common sense, good heart, curiosity, perseverance, all of those positive kinds of things. I really wanted to model for kids that there aren’t magic answers. There is no fairy dust. We can’t wave a wand and make things happen, and we don’t do it alone. That’s not how it works in the real world. How we relate with others, what we learn and have inside of us is what will help us succeed. It’s our very ordinariness that makes us successful.”