"The title is a reference first and foremost to all the light we literally cannot see: that is, the wavelengths of the electromagnetic spectrum that are beyond the ability of human eyes to detect (radio waves, of course, being the most relevant). It’s also a metaphorical suggestion that there are countless invisible stories still buried within World War II — that stories of ordinary children, for example, are a kind of light we do not typically see. Ultimately, the title is intended as a suggestion that we spend too much time focused on only a small slice of the spectrum of possibility."
It takes place before and during World War II in Germany and occupied France and tells the parallel stories of Marie-Laure, a young, blind French girl and Werner, an orphaned German boy with great skill in science and fixing radios. When he fixes a radio for a Nazi official Werner is sent to a national school that trains boys for an elite unit that will serve the Third Reich. The school is a brutal experience.
Marie-Laure lives with her father, a locksmith at the Muséum National d'Histoire Naturelle in Paris. It is there that Marie-Laure hears the story of a precious stone in the museum's collection that has a curse attached to it. Marie-Laure's loving father makes puzzles for her of the streets and houses of Paris meant to teach her how to navigate the city. She also learns to read braille and books provide a great deal of solace to her during soul-destroying times.
The stories of Marie-Laure and Werner zigzag back and forth between past and future, bringing their lives closer together.
Eventually both Werner and Marie-Laure end up in the French coastal town of St. Malo. Werner is a Nazi soldier whose unit was sent there to trace the sender of intelligence radio broadcasts. He becomes trapped in a bombed out building. Marie-Laure and her father fled to St. Malo during the fall of Paris. They carry the cursed jewel with them. When her father is taken prisoner she stays on with her reclusive great uncle Etienne who is sending illicit radio broadcasts for the resistance.
There is another storyline that has an evil Nazi searching for the jewel. I found this thread unnecessary and distracting.
I listened to the audio version of this book on the treadmill. I found it easy to follow the story despite the frequent shifts in time and place. It's a good work of historical fiction that would appeal to a wide spectrum of readers.