Opening with the immediate aftermath of a bombing on a London tube near Elephant and Castle, this tells the tale of Alessa, one of the survivors and her discovery of deeper shadows in London.
Those shadows, or the "Shade" begin to follow Alessa around, adding a supernatural misery to her all too real PTSD. They are an oozing black mass, with lamprey-like mouths, drawn to misery and anguish. And since no one else can see them, she's more than a little worried she's going mad.
No one, that is, until two people from a survivors group therapy meeting, Casey and Tom, manage to let slip they've also seen hints of these creatures. And also possibly the man that helped her out of the Tube that day, who she's never seen since. Casey has been watching the shades for a very long time, and has developed something of an unhealthy fixation with them, whereas Tom is rather more happy-go-lucky, with an academic interest in the creatures.
The three begin to investigate what went on that day and what the shades are up to, and since this is a horror, they don't discover anything good.
I wasn't too impressed with this one, for a couple of reasons. The ending of the book is very similar to a big cultural touchstone of the nerdy type, (won't spoil it), and this didn't put enough of a spin on the idea to make me go "wow", rather than "seen that before". The Shades had a similar problem, not being sufficiently distinctive for me to be curious about what they might want or how they might achieve their goals.
Casey's craziness feels a little too unfocused, such that though there's a reason for everything she does, it's very hard to be interested in that reason. Similarly, I found Alessa annoyingly passive, with a considerable similarity to the protagonist of the recent Fever Dream, who spent most of the book watching what happened to them.
The writing's good enough, and it's an excellent examination of mental health (or lack of it), but this was one I finished because it was on the list, rather than any thrill about the plot.