Desire
Desire is a driving force in the novel: Ash and Christabel's desire for one another is what led them to take the risk of pursuing an affair, but the desire of various scholars to uncover the truth about what happened is what motivates much of the action of the plot. The novel's plot also makes it clear how one form of desire can generate another: Roland and Maud are at first driven by their desire to better understand the writers they love, but their pursuit of the mystery leads them to eventually feel romantic and sexual desire for each other. As Lisa Fletcher writes, "Roland and Maud’s dependence on the story of their Victorian counterparts; their romance is made possible by the secret Victorian romance they discover and pursue" (pg. 152).
Creativity
Part of what makes Ash and Christabel's affair so powerful is that they feed off of each other's creative energy and aspirations. It turns out that their relationship led to the birth of a child (and by extent, Maud's existence as a descendent of that child), but at first it seems like the major output of their love affair was the writings stimulated by their conversations and interactions. Most of the modern characters, significantly, are critics but not creators: their role is to analyze and mediate art produced by others. The desire to uncover the secret of Ash and Christabel's relationship takes on additional importance because it involves generating new knowledge, and therefore becomes aligned with a sort of creative process.
Interpretation
The novel makes it clear that there is almost always a gap between an original text or event, and how that text or event is later interpreted and understood. Part of why Roland and Maud are so eager to find out what happened between Christabel and Ash is because this information would change the way the biographies and writings of both poets have always been interpreted. The plot shows how the discovery of new information can lead to new understanding. However, it also hints that perfect interpretation is almost always impossible: even at the end of the book, the modern characters fail to accurately understand the significance of the blonde hair found in Ash's grave, and have a false understanding of what Ash knew and didn't know about his child.
Poetry
Part of Byatt's unique contribution in the novel is her inclusion of a significant amount of original poetry, written to imitate a style that could have been composed by Victorian writers. Since Byatt includes poems written by both Ash and Christabel, she has to create two distinct poetic voices. Poetry symbolizes a kind of intellectual freedom and desire to break free from constraints: for both Ash and Christabel, poetry is part of what draws them together and leads them to recognize kindred spirits in one another. When Roland spontaneously composes poetry after receiving several job offers, readers have the chance to observe how his intellectual quest has liberated him from relying on the approval of others.
Collecting
Ash is presented as a type of collector, due to the way he infuses his writing with references and allusions. The primary way in which collecting, however, becomes a theme in the novel is via the actions of the contemporary scholars. While Roland is at first judgmental about a desire to own things associated with famous figures, he cannot resist the temptation to steal the letters and keep them a private secret. Cropper is portrayed as a villain because of his insatiable desire to own everything related to Ash, but some drive towards collecting and owning animates all of the scholar characters. Even if they only own ideas and influences, their desire for control over the writers who interest them function as a kind of ownership and collection.
History
History, and the gaps between the record and the truth, is a major theme in the novel. At the start of the plot, the official history of the lives of the two poets is taken for granted and accepted as the true reality; part of the unsettling impact of Roland and Maud's discoveries is that it shows history can be altered, or proven to be false. The entire mystery plot hinges on a desire to correct the historical record to be more accurate: all of the scholars agree that if Ash and Christabel had a relationship, that needs to become documented as part of the historical record. However, as the flashback scenes reveal, the historical record can only provide facts, not the full extent of what those moments felt like at the time they were lived. Significantly, the postscript also shows that even though it seems like the mystery has been solved, the historical record will continue to be wrong, and no one can ever fully recapture the past.
Gender
Gender is an important theme in the lives of both the Victorian and the modern characters, showing how circumstances both have and have not changed. Christabel's desire for autonomy and creativity create challenges for her as a Victorian woman, and scholars rightly interpret much of her writing to be expressing frustrations with those constraints. Gender also comes into play in how her affair with Ash is more risky and consequential for her: she carries the burden of an illegitimate pregnancy and the decision to hide her child's existence alone. For the contemporary characters, Roland struggles with a sense of emasculation stemming from his lack of job prospects and economic autonomy. At the end of the novel, it is only when he has successfully completed his quest to solve the mystery, and secured a more stable future for himself, that he can speak openly of his desire for Maud, and she can reciprocate those feelings.
