Book Club's Jane Fonda, Candice Bergen and Mary Steenburgen have offered their heartfelt tributes to Diane Keaton following news of their costar's death at 79. "It's hard to believe...or accept...that Diane has passed," Fonda, 87, wrote via Instagram on Saturday, October 11. Keaton's spokesperson confirmed to People on Saturday that the actress died, though no further information was initially provided. Her family - which included two children, daughter Dexter and son Duke - "asked for privacy" in their time of mourning.