Apart from the time-travelling, the possibly sentient robots and gods and goddesses, not much sci-fi or fantasy here, but plenty of philosophy, melodrama and a little sexual violence. Jo Walton continues to pursue excellence in writing in this thought experiment of realising the Just City of Plato. To be honest, the ideals of the Just City are a bit shit and demonstrate once again why we shouldn't slavishly follows ideas from the Bronze and Iron Ages. Perhaps Walton subtly alludes to this with the demographic and centuries of origin of the Masters. Nevertheless, this is a thoroughly engaging and thought-provoking read, and you may ask yourself the question enunciated by Simmea that appears as the title of this review. Why indeed, eh? I look forward to reading the next book in the series and I hope we see more of the workers.