A ghost hunter is drawn into a conspiracy that blurs the lines between the living and the dead. Felix Castor, a freelance exorcist in London, takes on a case that seems straightforward: a wealthy client wants a haunting investigated. However, he soon discovers that the spectral activity is far more complex and dangerous than he initially believed, involving a shadowy organization and a plot that could unleash something terrible upon the city. The narrative unfolds through Felix's cynical first-person perspective, detailing his gritty encounters with the supernatural and the moral compromises he must make.

The Felix Castor series, of which Vicious Circle is a part, is generally praised for its dark, atmospheric take on urban fantasy. Critics often highlight Mike Carey's sharp prose and the compelling, world-weary voice of the protagonist, Felix Castor. The books are noted for their intricate plotting, blending supernatural elements with noir sensibilities and a strong sense of place in London. Readers appreciate the mature themes and the complex moral landscape the series explores, often finding it a refreshing departure from more conventional fantasy fare.