Her Fearful Symmetry by Audrey Niffenegger

In this signed edition, Audrey Niffenegger's spectacularly compelling second novel opens with a letter that alters the fate of every character. Julia and Valentina Poole are semi-normal American twenty-year-olds with seemingly little interest in college or finding jobs. Their attachment to one another is intense. One morning the mailman delivers a thick envelope to their house in the suburbs of Chicago. From a London solicitor, the enclosed letter informs Valentina and Julia that their English aunt Elspeth Noblin, whom they never knew, has died of cancer and left them her London apartment. There are two conditions to this inheritance: that they live in it for a year before they sell it and that their parents not enter it. Julia and Valentia are twins. So were the estranged Elspeth and Edie, their mother.