Phantom Limb

Emily and Elizabeth are identical twins, and what they mostly have in common is a childhood spent locked in a bedroom while their mother drank, left, and came back on her own schedule. They got through it by having each other, and that arrangement never really ended.

In the present, Elizabeth is severely depressed and Emily is her carer. It is exhausting and it is also the shape Emily's life has taken, and neither sister has much appetite for changing it.

Then Emily meets someone. Lucinda Berry uses that as the pressure point, and as the dependence between the twins starts to be tested, Emily's version of events develops holes. The book is written from inside a narrator who has been maintaining something for a very long time, and it is careful about how and when it lets the reader see what.