I had a slow start with this book - put off by some of the foreshadowing statements in the earlier chapters. And - when Gretl makes her pact with Mr. Darcy-Witt - I almost threw my iPad on the floor. But I’m wondering if that was the reaction Boyne was going for. Gretl one more time making a “deal with the devil”. 

Did not expect her to murder the abusive husband

This statement from Boyne in his afterword hit home for me:
Writing about the Holocaust is a fraught business and any novelist approaching it takes on an enormous burden of responsibility. Not the burden of education, which is the task of non-fiction, but the burden of exploring emotional truths and authentic human experiences while remembering that the story of every person who died in the Holocaust is one that is worth telling.

He chose to tell a very different view of the Holocaust story - and I think he did a good job. I haven’t read the story of Greta’s brother - and I think I will.