The Gentleman by Dianna Roman is a compelling blend of mystery, historical drama, and romance, set in the early 20th century. This novel not only provides a thrilling narrative brimming with deception and secret identities but also offers a poignant exploration of the societal norms and gender expectations of its time. Roman's work has surely set a new standard in the genre of historical fiction by weaving a deeply intricate plot with well-crafted characters, making it a memorable read.

The story revolves around Jonathan Avery, a wealthy and enigmatic nobleman, who is as famed for his impeccable manners as he is for his notoriety in London’s high society. His smooth navigation through high society contrasts sharply with the dubious circumstances surrounding his fortune, which is rumored to involve everything from exotic trade to espionage. Amid these swirling rumors, Jonathan's path crosses with Eleanor Hawthorne, a determined and intelligent young journalist with aspirations that stretch far beyond the confines of her societal role as a woman.

Eleanor's initial encounter with Jonathan is marked by her determination to unravel the mystery of his success, driven by a personal quest for professional recognition and her own complicated history with London's elite. This professional endeavor quickly transforms into a complex relationship that deftly becomes the central pivot of the novel. Roman impressively portrays the evolving dynamics between them, using their interactions as a canvas to explore themes of power, trust, and the pursuit of freedom in an age where both were heavily regulated by class and gender.

Dianna Roman's ability to render the period is noteworthy. Her London is a character in itself—foggy, mysterious, yet alive with the bustle of carriages and the murmurs of intrigue. The author’s attention to detail does not stop at her setting; it extends to her characters. Jonathan Avery is not simply a charming protagonist but a deeply complex one, whose polished exterior often conflicts with the tumultuous secrets he harbors. Eleanor, on the other hand, embodies the struggle of early feminist ideals in a world that is rigid and unforgiving to ambitious women. Her boldness and resilience make her one of Roman’s most enchanting characters to date.

Throughout the novel, Roman masterfully manipulates tension and pacing, ensuring that readers are constantly on edge, eagerly anticipating the characters' next moves. Her prose is eloquent and evocative, capable of both sweeping descriptions of opulent ballrooms and concise, tense dialogues that convey volumes of unspoken tension. The suspense is carefully balanced with the emotional depth of the characters’ personal journeys, providing a satisfying and multi-dimensional reading experience.

A particular strength of the book lies in its secondary characters, who are neither incidental nor superficial. Each character we meet, from the sly servant to the stoic matron, is vibrantly drawn and contributes to the larger tapestry of the story in meaningful ways. This attention to peripheral detail enriches the world Roman constructs and enhances the realism of the narrative.

Moreover, Roman’s exploration of societal norms goes beyond mere backdrop and becomes integral to the plot. Themes of social mobility and the disparity between wealth and poverty are not only mentioned but are pivotal to the motivations and actions of her characters. The romance between Jonathan and Eleanor, while central, does not overshadow these broader themes but rather serves as a conduit through which Roman examines the constraints and challenges of their individual worlds.

The novel's climax is both surprising and satisfying, delivering on the build-up with a deftly handled resolution that ties together the major themes and character arcs in a coherent and fulfilling way. Roman’s skill in not only crafting a believable resolution but one that resonates with the emotional and thematic build-up of her narrative is commendable.

In conclusion, The Gentleman by Dianna Roman is a robust and captivating novel that offers its readers a vivid peek into a bygone era woven with thrilling mystery, deep romance, and sharp social commentary. It stands as a potent testament to Roman’s skill as a storyteller and her ability to capture the nuances of human emotion and societal pressure in a time of rigid hierarchy and opulent deception. The book is highly recommended for anyone who enjoys historical fiction with a strong sense of place and well-rounded, compelling characters.