I'm never sure which of Stevenson's books I like best. I love her light, frothy novels - all of the Mrs Tim novels. Miss Bucle's Book and Miss Buncle, Married; The Four Graces and Anna and her Daughters. But I also love her more thougtful and thought provoking novels, especially The English Air.
I've read many books about the years and months leading up to the Second World War but I don't think any novel has made me think more about the futility of the conflict than Stevenson's novel. She describes so poignantly the relationship between the half German, and initially all Nazi, Franz, and his English family. He arrives in England as a spy, living with and completely misunderstanding and underestimating, his English family. Over the course of his visit he comes to understand the British psyche and, as he falls in love with his cousin, Wynne, he starts to question his indoctrination with Nazi ideals. He learns to love England.
I think that many readers underestimate D E Stevenson and label her books as "nice". They are certainly nice but there is also a lot of depth to her characters, their situations and the novels in general. There is a great deal more subtlety to her books than at first appears.