You have to read the first three books..great all of them the characters start from younge to growing up..read them all three times..
From Publishers Weekly
Lush, sprawling escapist fiction of the first order, the third installment of the Cazalet Chronicle opens in the spring of 1942 and continues the saga begun in The Light Years and Marking Time. Set in London and the English countryside, much of the story focuses on the eldest Cazalet cousins, Louise, Polly and Clary, as they exit their teens and take their first steps into adulthood. Former acting student Louise has been swept into a brilliant but chilly marriage to Michael Hadleigh, a glamorous portrait painter and aspiring Member of Parliament whose life is controlled by his powerful mother. Best friends Polly and Clary leave the cozy confines of the Cazalet's country home to begin what they hope will be terribly grown-up lives in London. While Polly mourns the recent death of her mother, Clary keeps a journal that she hopes to give to her father, who has been missing since the invasion of Normandy. Alternating with the cousins' stories are chapters devoted to the rest of the Cazalet clan, their friends and lovers, bringing readers up to date on the doings of adulterous Edward, his dutiful spinster sister Rachel, her loving best friend Margot Sidney and others. Howard creates a nearly palpaple world, peopled with the sort of well-conceived characters that linger long in the reader's mind.