The Rose Code by Kate Quinn

This chronicles the goings on at Bletchley Park during WWII. Three very different women answer the call to mysterious country estate, where the best minds in Britain train to break German military codes. Vivacious debutante Osla puts her fluent German to use as a translator of decoded enemy secrets. Imperious self-made Mab, product of east-end London poverty, works the legendary codebreaking machines as she conceals old wounds and looks for a socially advantageous husband. Beth, whose shyness conceals a brilliant facility with puzzles, spreads her wings as one of the Park’s few female cryptanalysts. Together they work to get tactical information from the enemy into allied hands, and so much of the book is about the work that went on there, but the ending has to do with a traitor to his country, a clever one at that, who has Beth locked up to keep her from revealing his identity, and we never really understand what motivated him beyond greed. The characters are based on people who existed, and so is designated as historical fiction, and I enjoyed reading a kind of light, fictionalized approach to real people in a real place.