Originally drawn from a podcast series (2018) which is still available online, 'Spines' is an entertaining horror/dark fantasy tale that manages to avoid the cliches of the Lovecraftian and, at least initially, gives us something more in the spirit of Robert W. Chambers.
Killen has a fertile mind. The early sections show an imagination well above the average even if, over time, it is hard to maintain the momentum as the tale heads towards a more conventional 'competing secret societies' story line and a final brief moment of depressingly fashionable politics.
The characters, especially Shan the human-plant hybrid created out of the dark plot's premise (secret manoevrings to unlock human genetic potential for 'gifts' through dark science), are strong. Killen can also write about love and longing without it getting in the way of the story.
Occasionally she offers us quite profound thought experiments that verge on the philosophical and there is a sense of evil that allows us to call this cosmic horror. Killen is one of the most intelligent speculative fiction writers I have come across recently.
The early promise is, however, not quite fulfilled.The story just goes on for too long and shifts from true horror - including some body horror - to young adult material almost set up for a Netflix series. Ultimately, it lacks discipline and it weakens over time.
But this should not put you off because it weakens from considerable strength. It is never dull or stupid. Right to the very end Killen is able to surprise with plot twists and turns and she wears her feminist and 'intersectional' predispositions lightly, intelligently and with evident talent.