Weird Girls: Her Fearful Symmetry - Audrey Niffenegger

A bad thing about dying is that I'm starting to feel as though I'm being erased. When Elspeth Noblin dies she leaves her beautiful flat overlooking Highgate Cemetery to her twin nieces, Julia and Valentina Poole, on the condition that their mother is never allowed to cross the threshold. But until the solicitor's letter falls through the door of their suburban American home, either Julia nor Valentina knew their aunt existed.

The twins hope that in London their own, separate, lives can finally begin but they have no idea that they've been summoned into a tangle of fraying lives, from the obsessive-compulsive crossword setter who lives above them to their aunt's mysterious and elusive lover who lives below them and works in the cemetery itself.