Personally, I loved Mr. Churchill's Secretary. Maggie is quick and spunky, the supporting characters actually do provide support, and the story itself is light enough for holiday reading but intense enough to keep my attention for the majority of a twenty-four hour car trip. The history is well-articulated and atmospheric without being an oppressive infodump, though I suspect that some historical liberties were taken in the interest of driving the plot; however, it was nothing that would make my inner history buff growl. Honestly, I like seeing strong, feminist characters ahead of their time, and I absolutely love seeing strong, feminist characters who are strong because of their intellect.
In short: fun story, fun characters, occasional deep moments, little to cause a mystery fan discomfort.