Rebecca gradually reveals the essential facts and conflicts that drive the story. While it draws from the Gothic tradition, the novel leans more towards a suspenseful mystery rather than being genuinely terrifying. Both the reader and the narrator discover Rebecca's tale at the same time, which reduces some of the book's more chilling aspects. The sexual and psychological themes are subtle, presenting minimal risk to young adult readers. Additionally, the tone and vocabulary of Rebecca are sophisticated; any reader who can fully understand the novel's complexities is likely mature enough to handle its subtleties.

With the iconic opening lines of Rebecca — "Last night I dreamt I went to Manderley again" — du Maurier delves into the complex relationship between the past and the present. For the main characters, Maxim and his second wife, these timeframes are intricately connected. The second wife's troubled history leaves her feeling vulnerable in her new marriage, while Maxim's past with Rebecca complicates his relationship with his new partner. Manderley, Maxim's ancestral estate, is a vivid symbol of this link between past and present. Rebecca's ability to enhance Manderley's allure forces Maxim to endure a marriage he detests. Ironically, his fixation on preserving his legacy ultimately causes Manderley's ruin. The novel implies that both holding onto the past and trying to escape it are fraught with danger. As the second wife comes to understand, true peace with time is achieved by acknowledging the past while living fully in the present.

Another prominent theme in Rebecca is the conflict between good, represented by Maxim and his second wife, and evil, embodied by Rebecca and Mrs. Danvers. Although good triumphs by the story's conclusion, Maxim and his new wife carry permanent scars from their encounter with malevolence. Interestingly, du Maurier demonstrates that passive, naive goodness is insufficient to defeat evil. When the second wife is timid and innocent, she inadvertently aids the forces of darkness. It is only when she becomes strong that she can help Maxim overcome Rebecca. Unfortunately, this theme is somewhat undermined by the second wife's motivation. Her desire to help Maxim defeat Rebecca stems not from recognizing Rebecca as a symbol of evil, but from discovering that Maxim never loved his first wife.

Loyalty is the central driving force for the characters in this book. This is most clearly seen in Frank Crawley, the business manager of Manderley, and Frith, the head butler. Crawley shows his loyalty by being friendly and engaging in conversation without reserve, yet he never fully reveals his inner thoughts. Mrs. de Winter perceives Crawley's allegiance to her but realizes that his loyalty to Maxim prevents him from being entirely truthful about his feelings regarding Rebecca. Frith's loyalty is equally deep, but he maintains a more detached demeanor due to his role as a servant, which keeps him uninvolved and unaware of the personal affairs of the de Winters.

Mrs. Danvers, like Frith, is a family servant, but her loyalty leads her to neglect her duties. She is devoted to Rebecca, the deceased family member, and in her attempts to honor Rebecca's memory, she shows disrespect to the current Mrs. de Winter. Initially, her loyalty appears as an annoying but almost admirable trait, such as when she insists that certain traditions be followed because "that is the way Mrs. de Winter wants it done," ignoring the fact that she is speaking to the new Mrs. de Winter. After the costume ball, her hostility becomes overt as she exploits the narrator's distress about fitting in by suggesting suicide, saying, "You tried to take Mrs. de Winter's place." Ultimately, Mrs. Danvers' dedication to Rebecca's memory prevents her from accepting the happiness of the new Mrs. de Winter and Maxim, leading her to set Manderley ablaze.

The narrator's main concern, however, is her fear that Maxim remains loyal to Rebecca's memory despite their marriage. She interprets his sadness as lingering grief for his late wife. His avoidance of the bedroom he shared with Rebecca, his reluctance to visit her cottage, and his anger when the narrator wears the same costume Rebecca once did all seem to suggest his unwillingness to let go of her memory. In the end, when Maxim confesses to hating Rebecca and having killed her, the narrator does not consider leaving him because of his crime; instead, she stays loyal to him throughout the investigation, motivated by her love for him.

The narrator's feelings of inadequacy largely arise from competing with the memory of a deceased woman. Her perception of Rebecca's character is pieced together from various hints: a book inscription, a formal schedule left in a desk, Mrs. Danvers' stories, and accounts from those acquainted with Rebecca. The most disturbing comparison occurs when Maxim's eighty-three-year-old grandmother, in a moment of senility, loses touch with reality and suddenly exclaims, "I want Rebecca, what have you done with Rebecca?" Several practical factors heighten the narrator's sense of rivalry with Rebecca, particularly upon learning about Rebecca's beauty and social grace. Moreover, the narrator feels she cannot measure up, as Rebecca, being a memory, is unblemished, whereas she, as someone alive, is naturally flawed. Rebecca's enduring influence at Manderley is evident in the decor she selected, her established routines and traditions (like approving the daily menu), and the admiration from visitors. Rebecca's presence haunts the narrator almost as if she were a ghost still residing in the house. "Sometimes I wonder," Mrs. Danvers remarks while they examine Rebecca's belongings, "Sometimes I wonder if she comes back here to Manderley and watches you and Mr. de Winter together."

Ironically, the specter of Rebecca that looms over Manderley is more terrifying than sorrowful. Maxim de Winter recalls her as a vindictive woman who maintained a deceptively sweet public image. If he is haunted by her, it is due to his internal conflict over the guilt of having killed her, not because he longs for her. Frank Crawley's reluctance to discuss Rebecca, which the narrator mistakes for hidden affection, actually arises from discomfort because Rebecca had made unwelcome advances toward him, putting him in an awkward position. Beatrice and Giles find it difficult to speak openly about Rebecca since they both know she seduced Giles, leading them to default to polite compliments out of uncertainty. In the formal British setting of this novel, it seems more fitting to speak kindly of the dead than the living.

One of Daphne du Maurier's most impressive achievements in this novel is persuading readers to believe in the murderer's innocence and the victim's guilt. Within the novel's moral framework, several reasons are presented to justify why Rebecca deserved her fate. Firstly, she is portrayed as both cruel and deceitful. Maxim explains, "They all believed in her down here, they all admired her, they never knew how she laughed at them behind their backs, jeered at them, mimicked them." Mrs. Danvers further highlights Rebecca's duplicity by dispelling Favell's belief that Rebecca loved him: "Love-making was a game with her, only a game. She told me so. She did it because it made her laugh." Another reason Rebecca is seen as deserving her fate is her promiscuity. As the truth is revealed, it becomes clear that she was involved with or attempted to seduce several men, including Favell, Crawley, Giles, and likely many others, first in London and increasingly at her Manderley cottage, where she invited men for "picnics." Additionally, Rebecca's perverse behaviors, though not detailed in the book, are hinted at by Maxim, who shudders and says, "I shall never repeat to another soul." The ultimate transgression that compels Maxim to shoot her is her threat to bear another man's child and claim it as Maxim's, ensuring the child would inherit Manderley: "And when you died Manderley would be his. You could not prevent it. The property's entailed."

Maxim's perceived innocence in killing Rebecca stems from the selfless motivation behind his actions. He is not acting to protect himself but to preserve Manderley's reputation, which Rebecca's actions threaten. To the narrator, Maxim's purity of heart, his love for her, and his commitment to Manderley outweigh the act of murder. Ultimately, it is revealed that Maxim is less guilty than initially believed because Rebecca was suffering from cancer and would have died soon regardless. Another factor lessening Maxim's culpability is his suspicion that Rebecca intentionally provoked him to shoot her, seeking a swift, painless death and intending to burden him with guilt for doing what cancer would have done in a few months. Readers are left with the impression that Rebecca was truly guilty, while Maxim, who killed her and disposed of her body at sea, is portrayed as a victim of circumstances.