Tides of Time, a novel by Lexi Ostrow, is an intriguing blend of fantasy, romance, and mystery that promises to take readers on an exhilarating journey through time and emotion. Ostrow, known for her ability to weave complex narratives with engaging characters, delivers yet again with a story that not only entertains but also provokes thought regarding the constructs of time and the intricacies of human relationships.

The novel introduces us to Cassandra, a young woman with a life that seems utterly ordinary until she inherits an ancient amulet from her grandmother—a relic that bestows upon her the unsettling ability to witness historical events as if she were living them. This power is both a gift and a curse, thrusting Cassandra into the depths of history’s most tumultuous periods, but also allowing her to experience the most intimate, unrecorded moments of human interaction and emotion.

Ostrow's narrative structure in Tides of Time is particularly commendable. She expertly juggles multiple timelines, ensuring that the transitions are smooth and each period is given sufficient depth to maintain authenticity. From the gritty streets of Victorian London to the serene but rigid courtyards of feudal Japan, the settings are vividly described, bringing each era to life with meticulous detail and rich, atmospheric prose.

Central to the novel’s plot is the evolving mystery of why Cassandra has received this gift and what it ultimately means. The mysterious element intensifies when Cassandra stumbles across Ethan, a man whose fate seems inextricably linked to her own through the sands of time. Ethan, who also possesses an item similar to Cassandra’s amulet, is both a protector and a mystery, his past riddled with secrets that Cassandra must uncover.

The romance between Cassandra and Ethan is crafted with both sensitivity and intensity. Ostrow does not shy away from the difficulties their unique situation presents, making their moments of joy, conflict, and tenderness resonate all the more with the reader. Their relationship, fraught with challenges thanks to their connection through the amulets, provides a compelling narrative drive, pushing the story forward as they navigate not only their feelings but the implications of their encounters across different times.

Another aspect where Ostrow excels is in her portrayal of the secondary characters. Each character, no matter how briefly they appear, is drawn with precision and purpose, adding layers to the story’s main events and providing broader social and historical context that enriches the main plot. Whether it's a 19th-century street urchin or a wise old sage in ancient China, each character contributes meaningfully to Cassandra and Ethan’s understanding of their powers and their purpose.

In terms of themes, Tides of Time delves deep. It explores the notion of predestination versus free will, the impact of history on individual destiny, and the eternal question of what it means to have control over one’s fate. Through Cassandra’s eyes, readers are forced to confront these philosophical questions, making the journey not just one of external adventure but internal discovery as well.

The novel’s climax is both dramatic and satisfying, tying together the numerous threads of the plot in a conclusion that is both unexpected and fitting. Ostrow’s skill in building suspense is evident, as she masterfully brings all the elements of her story to a head in a finale that pays off both emotionally and intellectually for the reader. The resolution of the mysteries of the amulets and the decisions Cassandra and Ethan make about their future are handled with a deft touch that leaves room for thought long after the last page is turned.

However, as enthralling as the narrative is, some readers might find the frequent shifts between times and locations a bit disorienting at first. It takes a keen attention to detail to keep track of the unfolding events and the historical backdrops which, while richly crafted, are numerous.

In conclusion, Lexi Ostrow’s Tides of Time is a compelling and beautifully written novel that fuses elements of different genres to create a unique and memorable reading experience. With its complex characters, thought-provoking themes, and vivid setting, it is a book that not only delights but also offers deeper reflections on love, destiny, and the power of time. An absolute must-read for fans of historical fiction and romantic fantasy alike.