Alexis Hall's The Affair of the Mysterious Letter is a delightful romp through a fantastical universe that pays homage to the classic detective stories of Sherlock Holmes while infusing them with a vibrant and imaginative twist. This novel is not just a pastiche; it is a creative reimagining that stands on its own, offering readers a unique blend of fantasy, mystery, and humor.

At the heart of the story is Captain John Wyndham, a character who serves as both the narrator and the lens through which we view the eccentric world of Khelathra-Ven. Having returned from a war in another universe, Wyndham is a man out of place, seeking stability in a city that defies logic and reason. His voice is reminiscent of Dr. Watson, providing a grounded perspective amidst the chaos. Wyndham's character is well-developed, and his growth throughout the novel is subtle yet significant. His initial reluctance and skepticism gradually give way to a sense of wonder and acceptance of the bizarre, reflecting the reader's own journey through the narrative.

Contrasting Wyndham's grounded nature is Ms. Shaharazad Haas, a consulting sorceress whose mercurial temperament and dark reputation make her an intriguing and unpredictable character. Ms. Haas is a masterful creation, embodying the archetype of the brilliant but eccentric detective while adding layers of complexity through her magical prowess and morally ambiguous nature. Her character is a testament to Hall's ability to craft individuals who are both larger-than-life and deeply human. The dynamic between Wyndham and Haas is one of the novel's strengths, providing both comedic relief and moments of genuine camaraderie.

The plot of The Affair of the Mysterious Letter is a whirlwind of adventure and intrigue, as Wyndham and Haas are drawn into a case of blackmail involving one of Haas' former lovers, Miss Eirene Viola. The narrative takes readers on a journey through the diverse and vividly imagined city of Khelathra-Ven, from the salons of the literary elite to the shadowy back-alleys and even to the mysterious prison of Carcosa. Hall's world-building is exceptional, creating a setting that is both fantastical and immersive. The city of Khelathra-Ven is a character in its own right, with its fluid reality and myriad dangers adding depth and richness to the story.

One of the novel's most compelling themes is the exploration of reality and perception. In Khelathra-Ven, reality is flexible, and the impossible is commonplace. This theme is woven throughout the narrative, challenging both the characters and the readers to question their understanding of what is real. Hall uses this theme to great effect, crafting a story that is as much about the nature of reality as it is about solving a mystery. The fluidity of reality in the novel allows for unexpected twists and turns, keeping readers engaged and on their toes.

Another significant theme is the nature of relationships, particularly those that defy conventional norms. The relationship between Wyndham and Haas is central to the story, but Hall also explores other relationships, such as the one between Haas and Viola. These relationships are complex and multifaceted, reflecting the diversity of human (and non-human) connections. Hall's portrayal of these relationships is nuanced and thoughtful, adding emotional depth to the narrative.

In terms of style, Hall's writing is witty and engaging, with a sharp sense of humor that permeates the novel. The dialogue is crisp and often humorous, capturing the essence of the characters and their interactions. Hall's prose is both descriptive and evocative, painting vivid pictures of the fantastical world while maintaining a brisk pace that keeps the story moving forward.

Comparisons to other works are inevitable, given the novel's homage to Sherlock Holmes. However, The Affair of the Mysterious Letter distinguishes itself through its unique blend of fantasy and mystery. While it shares thematic elements with works like Neil Gaiman's Neverwhere or Terry Pratchett's Discworld series, Hall's novel stands out for its originality and the seamless integration of its influences. The novel's humor and whimsy are reminiscent of Pratchett, while its exploration of reality and perception echoes Gaiman's work. Yet, Hall's voice is distinct, offering a fresh take on the genre.

Overall, The Affair of the Mysterious Letter is a captivating and entertaining read that will appeal to fans of fantasy, mystery, and classic detective stories. Alexis Hall has crafted a novel that is both a tribute to the past and a bold step into new territory. With its richly imagined world, compelling characters, and thought-provoking themes, this book is a testament to the power of storytelling and the endless possibilities of imagination. Whether you're a longtime fan of Sherlock Holmes or new to the genre, this novel is sure to delight and surprise.