I'm writing a sci-fi book at the moment. Somehow I've come much further than any of my other book writing attempts, including one that I actually (self)-published.

I use Sublime Text, sometimes in distraction free mode, but usually not because I often want to Google sciencey things.

I have a single file called "story.txt" that has all the important notes - the names, ages and visual descriptions of the main characters, a detailed (historical) timeline, and chapter outlines I wrote before I started when I knew roughly what the overall plot was going to be. The chapter numbering has changed drastically but the overall outline has stayed pretty true to the original idea.

I really like this system. Keep it simple and focus on writing!