Tormented Dreams, a novel by Poppy Flynn, arrives as a thrilling, psychological exploration deep into the mysteries of dreams and the mind's shadowy corners where the subconscious and reality blur. This book, encased within its intriguing premise and a promise of suspense, attempts to take its readers on a labyrinthine journey that is as disquieting as it is reflective.

The story is centered on Rachel, a talented yet reclusive artist who finds herself plagued by increasingly vivid and disturbing dreams. These dreams don’t just disrupt her sleep; they start bleeding into her waking hours, blurring the lines between what’s real and what's not. Her nightmares are characterized by a constant presence of a shadowy figure, whose intentions are mysterious and dangerously palpable. It’s this figure that propels Rachel to seek understanding and therapy, leading her to Dr. Simon Blake, a psychologist with his own deeply buried traumas.

The narrative style of Flynn is immersive, enveloping the reader into the mental disarray of Rachel. The book's strength lies in its ability to portray the frailties and vulnerabilities of human psychology. Flynn uses a rich, descriptive language that perfectly conveys the eerie and melancholic atmosphere surrounding Rachel’s life. Her dreams are depicted in a manner that they almost creep off the pages, sending chills down the spine. The intertwining of reality and illusion is handled with a finesse that's both commendable and unsettling.

However, the novel does falter in pacing. The first half of the book, while atmospheric, tends to drag with repetitive cycles of dreams and wakefulness that might test the patience of even the most dedicated readers. But for those who stick around, the second half gains momentum, peeling back layers of the story and characters that at first seemed inconsequential or overly mystified.

The development of Rachel and Dr. Blake’s relationship is one of the highlights of the novel, evolving from a professional interaction to a nuanced, intricate connection that drives much of the narrative’s emotional depth. As Rachel's therapy progresses, Dr. Blake’s own past comes to light and it becomes clear how their fates are intertwined. Flynn handles the sensitive subject of mental health with a careful, empathetic touch, bringing to light the complexities and challenges of dealing with past traumas.

Supporting characters are a mixed bag. Some, like Rachel’s concerned sister, serve well to advance the plot or provide crucial insights into the main characters. Others, however, feel underdeveloped and are occasionally relegated to plot devices rather than fully realized individuals. Moreover, Flynn’s ambition to weave complex dream sequences sometimes results in convoluted passages that can confuse the reader about what is happening and what it means for the protagonists.

The climax of Tormented Dreams is ambitious and aimed at delivering a twist that wants to be both shocking and enlightening. Without spoiling the outcome, it's sufficient to say that the revelation connected to Rachel’s dreams is a bold narrative choice, though it might divide readers on its plausibility and impact. The resolution feels somewhat rushed, begging for a deeper exploration or perhaps a more nuanced buildup. Yet, it delivers a psychological punch that fits well with the novel's dark, introspective tone.

In conclusion, Tormented Dreams is a potent journey into the psychology of dreams and the impact of unresolved traumas on our conscious lives—one that offers a lot of darkness but also glimpses of redemption. Poppy Flynn succeeds at drawing a vivid picture of a woman’s battle with her nightmares, both literal and metaphorical, crafting a psychological drama that falters occasionally in execution but still stands as a compelling read. Fans of psychological thrillers and narratives centered on mental health will find much to appreciate here, even as they might find themselves wishing for certain elements to be further fleshed out. Despite its minor flaws, the novel is a testament to Flynn’s ability to probe the darker aspects of the psyche—making it worth the read for those who dare to delve into the shadows.