Obviously, the ex - husband is a central character. His ex - wife is also a very important character as she is the one related to his regret. There may be friends or family members who either support or oppose his attempts at dealing with the regret.
In 'ex - husband's regret novel', a prevalent theme is the passage of time. The ex - husband looks back on the relationship with a new perspective after time has passed. Nostalgia is also a theme. He feels nostalgic for the good times in the relationship. And there can be a theme of moving on, where he has to accept the reality of the situation and move forward in his life, even with the regret.
If we assume that 'Ava and Rowan' novels are in the adventure genre, then themes could include exploration, facing challenges, and teamwork. Ava and Rowan might be exploring a new world or trying to solve a mystery together. They could face various obstacles along the way, which would test their friendship and their own capabilities. Another possible theme could be growth. As they go through different situations, they might grow as individuals and in their relationship with each other.
I'm not sure which specific 'Ava and Rowan' novels there are. You could try searching in a local library's catalog or on an online bookstore like Amazon. They might have some novels with characters named Ava and Rowan.
The sadistic ex-husband recommended the following novels:
1. The author of the book is Bei Xin. This was a story about a ruthless man and an indomitable heroine, full of complicated entanglements.
2. "My Neighbor Is an Ex-Husband" Author: The Second Brother is the General Attack. It was a story about an ex-husband and a neighbor, and the plot was thrilling.
3. "Love After Parting" by: Only this. It was a story about two people falling in love again after breaking up, full of heartbreak and pain.
4. Author: Yu Anzhi. This was a heart-wrenching story about an ex.
5. [Beautiful Fraud] Author: Ran Zhu. It was a story about fraud and revenge, full of suspense and tension.
Please note that the novels recommended above may contain heart-wrenching plots. It is recommended to read them according to your personal preferences.
The titles of novels about ex-wives and ex-husbands could be " After Abandoning "," Reborn Ex-Wife "," Return of Ex-Husband "," Reborn Parents ", and so on.