Looking for suggestions from anyone. I have posted in here before how I want to write a book but can never think of ideas. I like fire fighting, war history, and racing. Any suggestions to help someone out on how you come up with your topic, characters, etc..
I recommend browsing the writing discussion parts of the forums. There are already several threads on this topic, the one of how people come up with ideas, and others that might spark that story for you.
Combine your interests. Let's see....a motor cycle racing champion has to race through a blazing forest fire to reach a remote military outpost and warn them of an impeding invasion? Or if by "racing" you mean a runner, same thing but the jogger has to cross through a raging fire.
I brainstorm. Pick a central idea, war history as an example. Then keep asking yourself questions, what war, where does it take place, who is the hero, where does the hero live, do they have friends/family, what battles were they involved in, etc . Eventually you'll be able to start linking ideas and events together building a story. Hope that was helpful. Good luck.
For a setting/loose premise, you might consider America's 19th century fire fighting rivalries. In my opinion there's ripe storytelling material there. https://knowledgenuts.com/2014/05/02/when-firefighters-were-actually-violent-gang-members/
Read other books. Writing cant be forces. Everyone has something to say, but not everyone can write a novel. Write what you have ideas for and when the idea for a novel enters your head it will. Here is something very important every writer should know. If you force writing it becomes a source of stress. From that point on the thought of writing will cause you stress and you will be unable to write. So please just write what comes to mind.