Jennie and Josh Book have turned their talents for writing and animation into interactive storybook apps. Courtesy photo

"Mr. Cupcake has the Sprinkles," Jennie Book says, "is a hilarious, goofy story ... Parents will laugh out loud." Courtesy illustration

"A Shark Knocked on the Door" is based on the Book's son, Baker, and his grandmother's fondness for sailing boats down the gutter after a rain storm. Courtesy illustration