SAN FRANCISCO — Eric Hill, whose effort to entertain his young son with a simple drawing of a mischievous dog named Spot blossomed into a popular series of children’s books that have sold more than 60 million copies, has died at his home in central California. He was 86.

Hill died Friday at his home in Templeton after a short illness, said Adele Minchin, a spokeswoman for his publisher, Penguin Children’s Group.

His first book, “Where’s Spot?” — with its clean design, whimsical characters, and bold, bright colors — was an instant success with preschool children when it hit store shelves in 1980. It told the gentle tale of Spot’s mother, Sally, as she goes on a search for him around the house — but finds a hippo, a lion and other creatures along the way.

But before his first triumph, Hill faced a number of rejections because so many publishers were wary of his use of paper flaps to hide parts of his illustrations — an innovation that was considered unusual at the time. In one case, for instance, a child could lift a flap in the shape of a door to reveal a grizzly bear gobbling up honey in the hallway.

“Familiar as we are today with a children’s book market where flaps, pop-ups and all kinds of novelty and interactivity are taken for granted, it is hard to recall what an extraordinarily innovative concept this was in the late 1970s,” Minchin said in a statement. “At that time, Eric’s idea was so different that it took a long while before anyone was brave enough to consider publishing his first book about Spot.”