Maybe there's a scientist in the 'the air we breathe novel' who is researching the quality of air. And perhaps a young person who is starting to become aware of the importance of clean air due to some health problems in their family. There could also be a politician or a business owner who has to make decisions that impact the air quality in the area.
Since the novel is about the air we breathe, the main characters could be a diverse group. There might be a mother worried about the air her children are breathing, so she starts to get involved in local environmental groups. There could be an old man who remembers when the air was cleaner and tells stories to the younger generation about it. And there may be a group of students who are learning about air pollution in school and decide to take action, like starting a campaign to plant more trees to improve the air quality.
I'm not sure exactly as I haven't read it, but they could be ordinary people affected by air - related issues, like a factory worker exposed to pollution or an environmental activist trying to make a change.
I think the main theme might be about the importance of clean air. It could be exploring how the air we breathe affects our health, our environment, and our overall quality of life.
Since I haven't read the 'free to breathe novel', it's difficult to say. It might have a female lead who is fighting against a system that restricts her freedom. Or it could be a group of friends who together strive to reach a state of being free to breathe.
I'm not entirely sure as I haven't read 'Breathe a Ghost Story' specifically. But generally, in a ghost story, there could be characters like a protagonist who might be the one to encounter the ghost, perhaps a young person or someone new to the haunted place. There could also be secondary characters such as friends or family members who either believe or don't believe the protagonist's experiences.
Since I don't know the exact story, it could be a patient who was suffering from a breathing disorder as the main character.
Without having read the 'masters of the air novel', it's hard to say exactly who the main characters are. However, given the title, they might be ace pilots. There could also be ground crew members or instructors who play important roles in the development of these 'masters of the air'. Maybe there are some characters who are not directly involved in flying but support the 'masters' in other ways, like family members who provide emotional support or military commanders who assign them missions.
I'm not sure specifically without having read it, but it could be a young, ambitious person trying to make their mark in the world.
Since I don't have the details of 'love in the air novel', it's difficult to name the exact main characters. But generally speaking, in this kind of romantic novel, the main characters are the ones whose love story drives the plot. They are likely to be individuals with unique personalities and backstories. Maybe one is a bit of a dreamer while the other is more practical, and their differences and similarities will be explored as their relationship unfolds.
I'm not aware of the particular 'castle in the air novel' you mentioned. But likely, the main characters would be individuals who are either trying to build their 'castle in the air' or are caught up in the allure of someone else's. It could be a group of adventurers who set out on a quest based on a far - fetched prophecy, believing they can achieve the impossible. Or it could be a lonely figure who has an elaborate vision of a different life and is struggling to make it a reality.
Since I haven't read 'A Mouthful of Air Novel', it's hard to name the exact main characters. However, often in novels, the main characters are the ones with the most complex storylines. They could be a protagonist who is on a journey of some sort, maybe a personal or emotional journey. There might also be supporting characters that interact with the main character and help to develop the story further, like a friend, a family member or an antagonist who creates conflict.
I'm not sure as I haven't read the novel specifically. But they could be pilots, aircrew members, or military commanders involved in the air war.