I'm not sure specifically as I don't know which 'the secret novel book' you're referring to. It could be about mystery, love, adventure or many other themes.
Since we don't have details about this particular book, we can only guess. It could center around the idea of secrecy in different aspects. Maybe it's about a secret mission that changes the lives of the characters involved. Or it could be exploring the concept of secrets in human relationships, like a secret love affair that has far - reaching consequences for the people around it.
Since it's a 'royal secret' novel, one possible main theme could be loyalty. Maybe there are characters within the royal court who are torn between loyalty to the family and loyalty to the truth. There could also be themes of love and sacrifice, where characters have to make difficult choices because of the royal secrets. For example, a character might have to sacrifice their own happiness to protect the royal family's secret, or their love for someone might be put at risk because of the secrets that are starting to surface.
Not having read 'Secret Sanction A Novel', I can only speculate. It could be centered around secrecy and the implications of sanctions in a particular setting. Maybe it's set in a political or corporate world where there are underhanded deals and the main character has to deal with the fallout of these secret sanctions. It could also be a moral exploration of when and why sanctions are kept secret and what that means for the individuals involved.
It could be about a hidden love. Secret romances are a common theme in many novels, where characters keep their feelings hidden from others for various reasons.
The main theme might be about secrets that are intense or 'burning' in nature, perhaps secrets that are so powerful they have a major impact on the characters' lives, like secrets related to love, betrayal or family issues.
The main theme might revolve around self - discovery as well. The 'secret' could be something within the characters themselves that they are not aware of at first. As the story progresses, they gradually uncover this secret which could be related to their true identity, their desires, or their purpose in life. This discovery then drives the plot forward and affects their relationships with other characters in the novel.
I recommend Douluo's White-Armored Divine Dragon to you! The main character of this novel is called Tuoba Chen. There are indeed many web novels with the surname Xiao, right? However, this novel had nothing to do with the surname Xiao. However, it meets your requirements very well. The plot is mainly about the various things that Taba Chen, the grandson of the Sacred Dragon Sect's Great Elder, experienced after he cultivated to become a White-Armored Earth Dragon. It's very interesting and is a light novel that has been derived from doujinshi. I hope you like this fairy's recommendation. Muah ~😗
The main theme could be about the power of storytelling. Through the storyteller's tales, secrets are revealed and lives are changed.
Another possible theme could be loyalty within the family. The family secret could put the loyalty of family members to the test. For example, some members might want to keep the secret hidden while others think it should be revealed, which could create conflict and show different levels of loyalty among them.
Since I haven't read the novel, it's hard to say for sure. But based on the title, it might be about a secret that the main character has.
The main theme is likely secrecy in a relationship. Since it's called 'the wife's secret novel', it probably delves into the consequences and implications of a wife having a secret.