Jilly Cooper, the bestselling British author known for her chronicles of class and sex in risque novels, including “Rivals” and “Riders,” has died, her agent and family said on Monday. She was 88. The author died Sunday after a fall, said a statement from literary agency Curtis Brown, which represented her. “Mum was the shining light in all of our lives,” her children, Felix and Emily, wrote. “Her unexpected death has come as a complete shock.” Queen Camilla, the wife of King Charles III, called Cooper “a legend” and recalled seeing the author recently at a book festival. “I join my husband, the King, in sending our thoughts and sympathies to all her family. And may her hereafter be filled with impossibly handsome men and devoted dogs,” Camilla wrote.