TV late-night talk show host Jay Leno has signed to do a children's picture book for S&S Books for Young Readers, where president Rick Richter signed him with agent Amanda Urban at ICM and Byron Preiss, of his own company, which is producing the book. It's called If Roast Beef Could Fly and is based on a true story from Leno's childhood of a backyard barbecue that turns wild. The pictures will be done by noted illustrator S.B. Whitehead, and the book is set for next summer.