By Jane Yolen. (The books are Sister Light, Sister Dark and White Jenna.)
I find I have less and less to say. I may have been prejudiced ahead of time (I read reviews on Amazon, of course), but even if Skada is in this story it doesn't seem like it tells her story.
Jenna is raised in a Hame, a sort of convent of all women who possess the secret of calling the other side of their selves out of darkness, to accompany them as their "dark sisters" in moonlight and firelight. Each dark sister knows everything her light sister knows, and they are said to be in some way the same person, but references are made to them living in their own world of shadow when they are not manifested by their light sisters' sides. Skada seemed to be more than just Jenna's reflection, though, and it seems as if even Yolen admitted there was something wrong with their relationship: at one point, when she fades away because of a fire going out, Jenna fails to notice (she is asleep beside her), but the comment is added that "She never noticed."
The interspersed (fictional) historical commentary seemed a little bit too abrupt. I think I would have preferred an uninterrupted narrative.
I think definite potential existed to develop the relationship between Jenna and Skada, but it seemed more like Skada only served as comic relief. Whenever Jenna didn't feel like hearing her advice, she just walked away from the light that cast her shadow, and yet it didn't seem that she already knew what the advice was most of the time, indicating that if Skada wasn't a separate person, she was at least a hidden facet of Jenna's self. Jenna never seems to ask how her sister is doing or what she feels; Skada always seems to offer her advice unprompted or not at all.
I think this could have been worth reading and probably was for the potential of the idea, but the manifestation definitely leaves something to be desired.