Is it Science Fiction? There is nothing in it to say that it is not Fantasy in the sense of Alternate World fiction. The Doctor, who is the protagonist of one of the two parallel stories, seems to come from the Culture; she is an incursion from another more advanced society and in this very similar to Sarah Blundy in Iain Pears's An Instance of the Fingerpost. The society is less SFnal than medieval-fantasy, which Banks has done in Against a Dark Background and even more so here; it is quite primitive, arming itself with crossbows, has just invented the telescope, and still keeps slaves; there is suffrage but it is not universal (p.87 - merchants are franchised). It also feels slightly Ursula LeGuin-ish, and this may be connected with the names ('UrLeyn', 'Oestrile' etc.).