Another theme is obsession. The characters are often obsessed with each other to the point where they are willing to sacrifice their own freedom or well - being for the other person. For example, they might give up their friends, family or career just to be with the person they love in a way that seems extreme.
Resilience is also a major theme. Despite the harsh conditions of slavery, the characters in these stories find ways to love and hold on to hope. They show that love can be a powerful force that helps them endure the brutality and inhumane treatment. For instance, they might find comfort in each other's arms in the slave quarters, which gives them the strength to face another day. Love in these stories is often a form of resistance against the dehumanizing system of slavery.
Unrequited love is also a theme. Sometimes the 'love slave' character loves someone who doesn't love them back in the same way. This can lead to a lot of internal struggle and angst, like in the case of many unrequited love stories in literature and movies.
The idea of sacrifice is also prevalent. The vampire may have to sacrifice their nature, like not drinking blood, or the human may have to sacrifice their normal life to be with the vampire. This is often seen in how they deal with the vampire's vampiric instincts and the danger it poses to the human.
Resilience is another theme. Despite the difficult circumstances, the slave girls in these novels usually show great strength. In 'Beloved', Sethe has to come to terms with her past as a slave and still tries to build a life for herself and her family. She endures so much but still has an indomitable spirit.
Another theme could be the idea of forbidden love. Since the 'slave' status implies a certain social or situational restriction, the love that develops is against the odds. However, it's important to note that these novels should be read with a critical eye considering the historical and ethical implications of slavery.
Power dynamics. In these stories, the master has power over the slave, which creates a unique relationship structure.
Forbidden love is also a major theme. In vampire slave romance novels, the relationship between a vampire and a slave is usually frowned upon in their fictional societies. So the lovers have to overcome social and cultural barriers, which adds to the allure of the story. The vampires often have their own rules and taboos regarding relationships with slaves, and the human slaves may have their own fears and reservations about getting involved with a powerful vampire.
One common theme is the struggle for freedom. Elves, being slaves, often strive to break free from their bondage. Another theme could be discrimination, as they are slaves and likely face unfair treatment from other races. Power imbalances also play a role, with the masters having power over the elf slaves.
One common theme is power dynamics. There's often a struggle for power between the protagonist and other characters in relation to the harem. Another theme is loyalty, as the harem members show loyalty to the main character in different ways.
Another theme is redemption. Often the character in the position of power realizes the wrongness of the slave - like relationship and tries to make amends. This can lead to a very deep and emotional romantic connection as they grow together. In some novels, the slave character also rises above their situation through love.