On my trip I started (and finished) Sarah's Key by Tatiana de Rosnay.
Sarah's Key takes place both in modern times and 1942. Sarah is arrested in Paris in 1942 in the Vel de'Hiv' roundup. She locks her younger brother in a cupboard (their secret hiding place) to keep him safe, she tells him she will come back for him and takes the key with her (she thinks she will be home in a few hours).
On the 60th anniversary of the roundup, journalist Julia Jarmond, who lives and works in Paris, is asked to write an article about this awful day in French history. While she is researching, she uncovers a slough of family secrets that tie her to Sarah.
Though this book was quite sad, I enjoyed it, and read it fairly quickly. It was a good choice for a vacation read. I was mostly interested in the fact that I had no idea that anything like this had happened, as most people probably are not. It was the French police that were responsible for this roundup, and it is obviously something that they are not proud of.