But...now I'm going to go be all complicated and look at when defying reality feels like it goes a little too far for me.
Why? The characters are too darn nice.
In Victor's family, girls are educated just as well as boys. Interest in the arts is cultivated just as much as an interest in science. The rich family spends every Sunday cooking lavish meals for the serving staff!
Any one of these things I would have been okay with - heck, I'd probably be okay with all of them - if the characters weren't so damn smug about how enlightened they are. And, like SF dystopia XVI earlier this year, (so far) there's been no explanation of why this family is so magnanimous. Especially if you're a family with some sort of power, some tangible reason to keep the status quo, if you're going to break that status quo I wan't to know why.
Or? I don't want it to be acknowledged. If the Frankenstein's are wise beyond their years, that is awesome, but why not just show them being awesome? Why make them so aware of their awesomeness? If that awesomeness is integral to the plot somehow, then just show us them being awesome in contrast to evil horrible people who subjugate their women and/or servants and/or artists.
For me there's a difference between escapist literature (imagining a world that is better than the one we live in), and...I guess I would call this overeager literature. It emphasizes that the world MAY HAVE been bad, but look at these people who hold our modern values in this antiquated time!!!
Anachronism can be used well - slightly altering the order of events for better drama, bringing in an invention a few years early or a few years late, or setting aside some common bigotries in order to better get to the story you want to tell. But when anachronism is handled poorly, when that anachronism seems to become a plot point, or a point that overshadows the plot, I get turned off.
How important is historical accuracy to you in historical fiction? What do you think about characters holding 21st century values in settings that are decidedly not the 21st century?