Since I haven't read 'Remembrance Day A Novel', I can't say for sure who the main characters are. But if it's a story about remembrance, there might be an older character who has a lot of memories to share. Maybe there's a young person who is learning about the past from this older character. There could also be characters who were directly involved in the event that is being remembered, such as soldiers if it's about a war, or activists if it's about a social change.
I don't know as I haven't read the book. There could be a diverse range of characters though, like a war veteran perhaps if it's related to war remembrance.
Not having read 'Remembrance Day A Novel', it's impossible to name the exact main characters. However, considering the title, it's likely that there are characters whose lives are deeply intertwined with the idea of remembrance. There could be a character who has lost someone dear and the whole story revolves around their journey of remembrance. There might also be a character who is on a quest to uncover the truth about a past event, and through this exploration, the story unfolds. There could be supporting characters like friends or family members who either help or hinder this character's pursuit of remembrance.