Mary Jo Putney, or MJ Putney as she is called in her incarnation as a YA author, appeals to me because her characters are thinking, talking people first and foremost. They observe their emotions and often comment on them in a way I find endearing even when anachronistic or unlikely. This may seem odd in an author who concentrates on romance novels, but it also means that her characters tend to have real problems rather than silly misunderstandings, and that her books are full of people it wouldn't be painful to spend a cruise with.
Dark Mirror, her foray in YA fiction, builds on her dabbling with magic in her regency romance period. It's an alternate history that inserts its new ideas without changing anything else, which makes no sense if you think about it but does simplifies the setting. Magic is real, but the gentry in regency England regard it as crass, and any well-born child (such as Tory, our heroine) who displays talent gets shipped off to a strict boarding school that promises to stamp out such low-class tendencies. Meanwhile Napoleon rambles about in France, making some of the kids wonder if magic might help protect England from invasion. Suddenly Tory stumbles into a time portal, and finds herself in a pre-Dunkirk coastal village. Suddenly the idea of using magic to save one's country is no longer theoretical.
I liked the structure of the book -- just as Tory adjusts to life at boarding school the book suddenly jumps from a school story to a time travel adventure. This is the kind of thing that writing handbooks frown upon but that I loved as a child (and still enjoy). I enjoyed the calm pragmatism of the time travelers -- no hysteria about cars and light bulbs because these kids were magicians; what the contemps called science just seemed like arts they hadn't mastered yet. The dwindling of magic made no sense at all; it seemed clear to me that the portal was to an alternate universe, not just a future, but nothing in the text acknowledges this and it's not what the book is about anyway. As an adult, I did wonder where all the other magic users were; it didn't make sense that England got them all, but maybe that sort of thing gets covered in later books. This would have been a perfect book for the Read-a-thon, but I thought I couldn't renew it so I gobbled it up early. B+