Scrivener is a writing software designed to keep your book neat and organized as you write. It's like spring cleaning and opening windows, letting fresh air and sunlight into the writing-room of your mind. Everything is tidy, you can see your story in pieces, as a whole, from various angles. It's a delight!
I'm a meticulous plotter and outliner. I need color-codes, charts, maps, and order wherever I can get. Writing is a sticky business, and my thoughts get muddled so fast. Plots twist and tangle, ideas play hide-and-seek, multiply, fight, change, lose significance, gain importance--it's exhausting to keep track! Scrivener helps keep all of that in check. $40 well spent. (Website here.)