Another theme could be about redemption. Maybe the character Landon is trying to redeem his or her lover who has a dark past as a killer. It could be a story of trying to change someone for the better.
It could also be about the power of love to overcome fear. If someone is in love with a killer, they would have to face a great deal of fear, and the novel might explore how love can help them deal with that fear and the dangerous situation they are in.
I'm not sure about a specific novel named 'landon my killer lover novel'. But some popular mystery and thriller novels with a bit of a romantic element are 'Gone Girl' by Gillian Flynn. It has a complex relationship and a lot of mystery around the characters.
Another theme could be acceptance. The human in the story has to accept the fact that their lover is a ghost, with all the strangeness and limitations that come with it. Also, the ghost may have to accept that the human has a different way of life. There might also be a theme of loneliness. Maybe both the human and the ghost were lonely before they found each other, and their relationship fills that void in their existences.
One possible theme could be loss. Since it's about a first lover who is now like a shadow, it might be about the loss of that relationship and the feelings associated with it.
Well, it could start with a new relationship where one partner is overly possessive, which is the early sign of the stalker - like behavior. The stalker - lover then starts to isolate the other person from friends and family. As the story unfolds, the other person tries to escape this toxic relationship. In response, the stalker, feeling a sense of loss of control, becomes a killer in a desperate attempt to stop the person from leaving.
One possible theme could be secrecy itself. The fact that it's a secret lover implies that there are things that need to be hidden, like perhaps the relationship goes against social norms or workplace ethics.
Love is surely a main theme. It likely explores the different aspects of love between two people who are in a relationship that could lead to marriage.
One possible theme could be betrayal. If the mother has a lover, it likely involves a betrayal of the family unit or her relationship with the father figure. This can lead to a breakdown of trust within the family.
Love, of course. It's in the title, so it's likely a central theme. Maybe also the idea of a journey, as it's a 'path'.
Another feature could be a complex plot. Maybe there are obstacles in the relationship that the lovers have to overcome, like family differences, misunderstandings, or external forces trying to keep them apart. This would make the story more engaging and keep the readers on their toes, eager to find out how the lovers will ultimately be together.
Growth is often a theme in such novels. After the experience with the previous lover, the characters usually grow and change. They learn from the relationship, become more mature, and might approach future relationships differently.