I read this a while back, and then we went to see Niffenegger at the Edinburgh Book Festival a week ago and it spurred me into a reread.
It's a strange book, but I liked it, and more so the second time around. It has one major character, Martin, who has OCD to the extent that he can't leave his home, who apparently is based on one of Niffenegger's exes (along with a lot of her characters, by the sound of it). It's a bad sign of the way writing is that we should be grateful for these things, but I really was glad that he was highly intelligent, creative, charismatic, sexy, and generally sympathetically portrayed. There is another main character, Valentina, who is a mirror image twin with situs inversus (internal organs reversed), heart trouble, and asthma. There is a fairly sensitive exploration of the difficulties that can arise when a relative of partner ends up being someone's caregiver with both of these characters, showing both the loving side and how fucked up it can get, with intriguingly messed-up power situations. Julia, the other twin, is in a stiflingly close relationship with Valentina. There's a point when someone says to her, "You know, Valentina would do better if you left her to her own devices," and Julia replies, "I know, but I can't." The relationship Julia forms with Martin, where she voluntarily takes on a caregiving role to some extent, is somewhat odd, but healthier and more productive than her relationship with Valentina, perhaps because there's more distance between them.
There's also a ghost, Elspeth, and some of her experiences mirror the disability/illness issues the other characters face, in terms of learning to deal with various limitations and indeed impairments. Elspeth is confined to her flat, and at first she is amorphous and barely thinks at all. It's a bit like how you can feel when utterly conked out by certain meds. She gradually learns how to control herself, how to get more of her identity back, although she is still extremely frustrated at how little she can do and how incredibly difficult it is to communicate with the living. It takes her an incredibly long time to learn how to move physical objects a tiny amount, and even so it still takes the twins, who are living in her flat, a while to realise that she is really there. I've had days when communicating felt like that. Of course, while Elspeth gradually gains power throughout the novel, she also gradually loses her humanity and doesn't really notice that happening. The end of the novel is shocking and surprising, and you really have to rethink which of the characters you like and approve of as things change.
- Niffenegger, Her Fearful Symmetry