Historical fantasy retelling the legend of Perseus and Andromeda and the killing of Medusa; the fantasy aspects are mentioned early, but become more prominent later on, which feels a little unbalanced; there's so much more at the end than the beginning.
Good on the politics of the Greek city-states as the Achaians come from inland and displace the old, tribal, matriarchal societies with a more patriarchal and militaristic culture; Halam has some anachronistic touches, sometimes just with language ("refugees" sounds so modern, even if the concept is old) and sometimes not (Danae's adoptive father invents spaghetti). Sometimes this was striking, bringing the harsh nature of events home ("refugees") and sometimes it just felt silly (spaghetti). What's most striking is the Ethiopian princess Andromeda, who takes the symbolic Phoenician script a step further and invents alphabetic writing, although useful as it is I'm not convinced it's necessary for civilization (China seems to have done okay without it). But there's some gorgeous and playful stuff about invention here, as well as some serious stuff about cultural conflict and the small starts of world changes.
Also, this is probably the least depressing of Ann Halam's children's books I have read since The Daychanger trilogy.