Riley Sager's Lock Every Door is a gripping psychological thriller that masterfully intertwines suspense, mystery, and a touch of horror, all set against the backdrop of a luxurious yet ominous Manhattan apartment building. The novel's premise is immediately intriguing: a young woman, Jules Larsen, finds herself in a seemingly perfect job as an apartment sitter at the Bartholomew, a building steeped in history and mystery. However, the allure of the Bartholomew quickly gives way to a chilling narrative that keeps readers on the edge of their seats.

At the heart of the story is Jules, a character whose personal struggles and vulnerabilities make her both relatable and compelling. Recently heartbroken and financially destitute, Jules is a protagonist who embodies resilience and determination. Her decision to accept the apartment-sitting job is driven by desperation, but it also marks the beginning of a journey that forces her to confront her past and her fears. Sager does an excellent job of developing Jules as a character, allowing readers to empathize with her plight and root for her as she navigates the increasingly sinister environment of the Bartholomew.

The Bartholomew itself is a character in its own right, with its opulent facade hiding a dark and twisted history. Sager's vivid descriptions bring the building to life, creating an atmosphere that is both enchanting and foreboding. The rules imposed on Jules—no visitors, no nights away, no disturbing the other residents—add to the sense of isolation and unease that permeates the novel. As Jules delves deeper into the building's secrets, the Bartholomew transforms from a place of refuge to a labyrinth of danger and deception.

The supporting characters in Lock Every Door are equally well-crafted, each adding depth and complexity to the narrative. Ingrid, the fellow apartment sitter who befriends Jules, serves as a catalyst for the unfolding mystery. Her disappearance sets off a chain of events that propels Jules into a race against time to uncover the truth. The residents and staff of the Bartholomew, with their own secrets and motives, contribute to the novel's suspenseful atmosphere. Sager skillfully weaves their stories into the larger narrative, creating a tapestry of intrigue that keeps readers guessing until the very end.

One of the novel's most compelling themes is the exploration of trust and betrayal. Jules's journey is marked by her struggle to discern friend from foe, a challenge that is exacerbated by the deceptive nature of the Bartholomew and its inhabitants. This theme is further underscored by the novel's exploration of the lengths to which people will go to protect their secrets and maintain their facades. Sager's ability to create tension and uncertainty around these themes is a testament to his skill as a storyteller.

Lock Every Door also delves into the concept of identity and the impact of past trauma. Jules's connection to Ingrid, who reminds her of her lost sister, adds an emotional layer to the narrative. This connection not only drives Jules's determination to uncover the truth but also forces her to confront her own unresolved grief and guilt. Sager handles these themes with sensitivity, adding depth to the novel's psychological elements.

In terms of pacing, Sager expertly balances moments of intense action with quieter, more introspective scenes. The novel's structure, with its alternating timelines and perspectives, adds to the suspense and keeps readers engaged. The gradual revelation of the Bartholomew's dark history is skillfully executed, with each new discovery building on the tension and intrigue.

Comparatively, Lock Every Door shares thematic similarities with other works in the psychological thriller genre, such as Shirley Jackson's The Haunting of Hill House and Sarah Waters' The Little Stranger. Like these novels, Sager's work explores the idea of a seemingly benign setting that harbors malevolent forces. However, Sager's modern twist on the haunted house trope, combined with his focus on character development and psychological depth, sets Lock Every Door apart as a unique and compelling read.

Overall, Lock Every Door is a masterful blend of suspense, mystery, and psychological insight. Riley Sager's ability to craft a narrative that is both thrilling and thought-provoking makes this novel a standout in the genre. With its richly drawn characters, atmospheric setting, and intricate plot, Lock Every Door is a must-read for fans of psychological thrillers and anyone who enjoys a good mystery with a touch of the macabre. Whether you're new to Sager's work or a longtime fan, this novel is sure to leave a lasting impression.