Mr. Churchill's Secretary by Susan Elia MacNeal

In 1940, American-raised Maggie Hope has returned to her birthplace of England to sell her grandmother's home, but with no one wanting to buy it and a war on, she decides to stay and gets a job at No. 10 Downing Street as a secretary. Maggie is overqualified for the position with a college degree from Wellesley and acceptance to the PhD program at M.I.T. Because of her intellect, she finds herself working closely with Prime Minister Churchill and involved in combating both the IRA and the Nazis. Being back in England also allows Maggie time to reflect on her parents, who died in a car accident when she was very young. Eventually, it becomes clear that those around her are keeping secrets about her past. In this series debut, MacNeal writes a mystery full of historical detail about daily life in London during World War II, along with creating an engaging and interesting main character.