While I didn't think this was as stellar as All the Light You Cannot See, it's not really a fair comparison. These are novels with vastly different approaches.
All the Light You Cannot See is mostly about the similarity of experiences of citizens and soldiers on both the German and French sides. The Nightingale relies on true-life stories of French resistance fighters, those in it from the beginning and those who had resistance thrust upon them. I will completely agree with anyone who says that Hannah knows how to weave stories, because she kept me reading late at night, wondering what the next heart-stopping or unthinkable circumstance would be. I admire how she told parallel stories - both sisters in distinctly different circumstances and how they survived - and brought them together and apart as it befitted the storyline. She has built something wonderfully complex as well as mostly recognizable, and that is worth some kudos (for bravery, if nothing else).
I did wonder at her choice to include the concentration camps towards the end of one of the sister's storylines. This was barely 15 pages long, and that kind of short shrift is surprising in a WWII novel, if it's being told at all. I felt a little like Hannah had run out of steam but that she felt she had to add this in or it wasn't close enough to the truth of WWII, in general.
I also thought it was a bit of a cheat not to let on to which sister was telling the tale from old age, because I don't think that layer of mystery was necessary or added to the plot in any way. It also made me snort that a dying woman would insist on walking around Paris in high heels. But I did live in Italy, and that does seem to be the case on the continent. Nothing would keep you off heels on cobblestones, not even if you were dying!