Serpentine is a young adult fantasy novel with a historically-inspired Chinese setting that revolves around two major themes. The first is the domestic story of the protagonist Skybright, a foundling who is handmaiden and companion to the well-born Zhen Ni, as both of them stand at the edge of womanhood. The external peril is an invasion of supernatural creatures who have found an opening into the mortal world and are being fought off by a martial order of monks. A major theme of the several braided plot lines is the consequences of concealing your inner nature from those closest to you. Zhen Ni's secret is her romantic love for other girls, first turned toward Skybright and then toward a visiting friend who returns the interest more enthusiastically. But Zehn Ni's fate is to marry well and produce children, and she can only conceal her desires for so long. Skybright's secret is more drastic: she is a serpent demon, with a tendency to shift between human and demon form at unexpected times. And the young man she's feeling a growing attraction to is currently fighting demons with the monks...
I enjoyed the book, particularly in how it incorporated issues of sexuality within a historic culture, and realistically portrayed the various social power differentials between the characters: Skybright's anomalous relationship to Zhen Ni as both "like a sister" yet with no future except to be her servant; the conflicted relationship between Zhen Ni and her mother (who it is hinted may have had a "special friend" in her own past that she had to give up); and the relationship between Zhen Ni and her lover Lan. Zhen Ni is frustratingly self-centered in all of these, but realistically so, given her status and upbringing, though I felt that her actions in the latter part of the book felt more plot-driven than character-driven. But this is Skybright's story, so the major conflict is in her growing understanding and acceptance of her demon heritage and her decisions about how to use that to fight for and protect the people she loves.
I don't think it's fair to note that I was a little put off by some aspects of the prose, because I'm not the target audience from that point of view. The language was a bit simple and did a bit too much explaining, but the setting was well rendered and vividly imagined. If the girls spend a lot of time agonizing over situations that could be resolved with some clear communication and a willingness to compromise...well, that's something in the nature of being a teenager, I suppose.
The story concludes with no happy endings for any of the various romances (no tragedy, but no happiness) and with a large handful of pending plot threads that are presumably taken up in Sacrifice, the sequel.