You can read the Goodreads summary here.
Andi is seriously depressed. She blames herself for the death of her younger brother and her pills don't make her feel better anymore. She's contemplated suicide a few times and is starting to flunk out of her exclusive high school in Brooklyn when her father announces she will be joining in him Paris, France for three weeks while her mother is admitted to a hospital for psychiatric treatment. Rough stuff. But when she gets to France she discovers a mystery about a young boy, meant to be king, who died tragically and the young woman who tried to cheer him up.
I read Donnelly's A Northern Light this year and loved it, but had read less than glowing reviews about Revolution. I was concerned I wouldn't like it, but thankfully, I really enjoyed it. I thought Andi's life in Brooklyn, though depressing, seemed realistic and raw. I was happy for her to finally start enjoying Paris, though even there she had her ups and downs. The mystery part of the plot was fantastic as were the settings, which takes the reader from stuffy palaces to creepy underground catacombs to the simple cafe around the corner.
I didn't always care for the diary entries that were included. I enjoyed that it was set up in a way that I got to read along with Andi, but I felt like sometimes those entries could have been broken up differently. I also didn't enjoy the part of the novel where Andi appears to be time traveling. I rarely enjoy time travel in novels.
Jennifer Donnelly did a lot of research when writing this novel and it seemed pretty historically accurate, aside from the fictionalized parts, obviously. I really enjoyed this novel overall and I recommend it.