Seems likely that this was inspired by the reading of comic books. The narrator is likened to a "superhero" on several occasions (171, 287), and very specifically thinks "of a comic-book hero: Batman or Daredevil. Silhouetted in the ruined window, King Rat looked like a scene-setting frame at the start of a graphic novel" (259). With those types of framing devices, the narrative proceeds as anti-superhero story (and of course there're no graphic components).
The subject matter is several strands of folklore, commingling in London. The revisionist folklore is, I suspect, simply the occasion for commentary on the setting. The narrative, for instance, reminds us that, regarding the setting, its "point of view was dangerous for the observer. It was only when it was seen from these angles that he could believe London was built brick by brick, not born out of its own mind. But the city did not like to be found out" (257).
That's only after the narrative "looked out over London at an angle from which the city was never meant to be seen. He had defeated the conspiracy of architecture, the tyranny by which the buildings that women and men had built had taken control of them, circumscribed their relations, confined their movements. These monolithic products of human hands had turned on their creators, and defeated them with common sense, quietly installed themselves as rulers. They were as insubordinate as Frankenstein's monster, but they had waged a more subtle campaign, a war of position more effective by far" (221).
But also: "a huge metropolis, deserted and broken, entropic, until a tsunami of air breaks over it, a tornado of flute clears its streets, mocks the pathetic remnants of humanity in its path and blows them away like tumbleweed, and the city stands alone and cleared of its rubbish. Even the ghost of the radio proclaims the passing of the people, a flat expanse of empty sound. The boulevards and parks and suburbs and center of the city were taken, expropriated, possessed by the Wind. The property of the Wind" (210).
That last bit concerns mostly an aspect of the novel, impenetrable to me, that functions as an elegy to certain forms of club music, much of it Jamaican in influence. The author makes some mention of the subgenre in the acknowledgements. No idea what any of that stuff is, however.
The principal antagonist is not really explained, and appears as Coleridge's Iago, "motiveless malignity."
The narrator is otherwise pulled into an alternate London, "melted into the interstices of the city" (163), pregnant but not otherwise described.
Several references to fascist dictators appear gratuitous at the time, but find purchase in the epilogue, which is cool, but not necessarily inexorable, considering the foregoing narrative.
The best part of the narrative is when the narrator befriends a homeless woman, which is not explained--but the implication, it seems, is that the narrator, for all the supernaturalism of his situation, is a homeless person, consigned to the sewers, rooftops, and other urban interstices. The novel doesn't become tendentious advocacy, but it's hard to miss the presentation.
Recommended for students of revisionist folklore, disciplined funambulists, those who resist "the poetics of the city" (237).