Whose memory can you trust?

Most siblings have a complicated relationship to some degree.  That potential conflict can be even worse when the siblings are twins.  Which twin is The Good Sister in Sally Hepworth's novel is the central question. Fern and Rose are living in Australia and each facing their own challenges.  Fern has sensory processing disorder and cannot abide loud noises or bright colors or crowds.  She also has problems recognizing social cues and is very blunt in her interactions with others.  Still, she is a very competent employee at her job in the local library and she maintains her own apartment.  Rose is married but unable to conceive a child.  Things aren't helped by the fact that her husband has taken a temporary job on the other side of the world in London.

The chapters alternate between Fern's day-to-day observations and a diary being kept by Rose where she discusses her own problems, her concern about Fern, and her memories of growing up with an unpredictable, vindictive mother.  

Fern decides that she can help Rose out by having a baby for her.  In her usual fashion, she thoroughly researches how she might go about this, and decides that the best way is to have a casual relationship with a stranger and conceive the old-fashioned way.  Luckily, a potential partner soon emerges in a library visitor she dubs "Wally" due to his resemblance to the main character in the "Where's Wally (Waldo to us Americans) books.  Wally has been living in the United States, but thanks to his mother's Australian citizenship, he's decided to relocate.  Since he's unsure of his future plans, for the moment he's living out of his van.  He meets Fern by coming to the library frequently to use their showers (?).  It turns out that Wally is a bit unconventional and has some similarities to Fern in the way he deals with the world.  What starts out as a casual fling soon becomes more serious.  This new relationship alarms Rose, but is she concerned for Fern's welfare, or that she might lose her influence over Fern?

While Fern and Rose are keeping a dark secret from their shared childhood, can they trust that their recollections of what happened are true?  I really enjoyed learning more about Fern and seeing how the other characters reacted to her somewhat unusual precautions to daily life.  It was also interesting to see how two people could have such different memories about the same shared events.

Disclaimer:  I received a copy of The Good Sister from NetGalley in exchange for this review