Scrivener is a project management tool for writers. It won't try to tell you how to write - it just makes all the tools you have scattered around your desk available in one application.
Scrivener provides access to the full power of the OS X text system - so you have total control over your text. Add tables, bullet points and images and view your text however you want. However, Scrivener is not a page layout program; Scrivener takes the unique stance that the way you view your text on screen may not be how you want to see it in print. Export italics as underlines; view your text in a Times New Roman font but export in a Courier font - or just export with your view settings: it's up to you. Define ranges of text as footnotes and they become footnotes when you export. Scrivener makes it easy to format your text after it is complete - leaving you free to focus on the actual writing.
Writing a book - or even a single short story or research paper - is about more than hammering away at the keys until done. Research, scrawling fragmentary ideas that don't seem to fit anywhere yet, collecting faded photos from old newspapers, shuffling index cards to find that elusive structure - most writing software is only fired up after much of the hard work is already done. Enter Scrivener: writing software that stays with you from that first, unformed idea all the way through to the first - or even final - draft. Outline and structure your ideas. Take notes. Storyboard your masterpiece using a powerful virtual corkboard. View research while you write. Track themes using keywords. Dynamically combine multiple scenes into a single text just to see how it fits. Scrivener has already been enthusiastically adopted by best-selling novelists and novices alike - whatever you write, grow your ideas in style.