The intrigue of heist novels can seldom be overstated, and The Duplicity of Thieves, penned by K. Moret, reaffirms this assertion with flamboyant narrative swings and complex character arcs, though it occasionally trips over its ambitious plot twists. This novel spins a dense tapestry of deceit, alliances, and betrayals that only the bravest can navigate without experiencing a certain degree of whiplash.

Set against the gritty backdrop of a fictional city, Meridian, which palpably breathes with life similar to that of Victorian London mixed with the harsh shadows of noir film, the novel introduces us to its protagonist, Elia Gremory. A master thief with a code of ethics that both hinders and defines her, Elia is a character wrought with contradictions. Moret's portrayal of Elia is layered, presenting a person who could easily be a hero in one light and a villain in another. What sets Elia distinctly apart in a genre crowded with antiheroes is her unwavering loyalty to her crew—a ragtag group of street-smart individuals each with a backstory that begs for its own novella.

The story wastes no time, plunging the reader into the midst of a high-stakes heist gone wrong. The opening sequence, cinematic in its execution, sets the pace for a book that's hard to put down. But it is not just the plot that entices; Moret's prose is sharp and decadent, weaving descriptions that paint Meridian in vivid hues of gray and gold. Readers will find themselves pausing to relish the lines that capture everything from the slick cobblestone streets to the piercing chill of the night air.

However, where the novel really shines is in its Byzantine plot developments. Elia is betrayed early in the narrative, which kicks off a chain reaction of events that compels her to navigate a web of intrigue involving the cream of Meridian’s societal elite. The twisted dance of maneuvering among allies and adversaries is where Elia thrives and where Moret demonstrates a keen grasp of suspense and tension. Each chapter seems to end on a cliffhanger, urging the reader forward.

But this intricate plotting is also where The Duplicity of Thieves occasionally stumbles. In its fervor to outdo each twist with another, the story sometimes borders on convoluted. Several secondary characters, who are intriguing in their own rights, do not get the developmental space they deserve. For instance, a rival thief, Lucan, with a charming mix of menace and mystery, often feels underused—his potential for depth overshadowed by the rapid progression of plot points.

Moreover, the dialogue, although crackling with intensity, sometimes slips into modern vernacular that can momentarily pull the reader out of the historically inspired setting. This isn’t enough to derail the narrative but is a noticeable hiccup in an otherwise meticulously constructed world.

Despite these minor grievances, the emotional reservoir of the novel remains potent. Elia's journey is not just external but introspective. Moret skillfully explores themes of trust, the dichotomy of freedom versus security, and the illusion of choice. These deeper queries haunt Elia, and by extension, the reader, nudging towards philosophical ponderings amidst thrilling escapades. It’s a complex weave of thrill and thought, action and introspection.

The climax of The Duplicity of Thieves is both exhilarating and satisfying, tying up enough loose ends to gratify but leaving sufficient strands loose to tease a sequel. The final heist, involving an artifact of legendary repute, is as grandiose as they come, blending a mix of tactical genius and the wild unpredictability of human nature that Moret has so impeccably captured throughout the novel.

In conclusion, The Duplicity of Thieves by K. Moret is a commendable addition to the heist genre, offering readers a dive into a rich world ruled by shadowy figures and elusive loyalties. While it occasionally overreaches in its complex plotting, it more than makes up for it with its vivid atmospherics, intriguing protagonist, and the visceral pleasure of a well-told tale of deceit. For fans of the genre, Elia Gremory’s adventures promise tension, introspection, and entertainment in ample measure, crafting a narrative that's as darkly glittering as the city of Meridian itself.