Ulysses is a wonderful writing and organization app. If you do any kind of writing on a mac, take a look. If it all seems a bit too much look at iA Writer, my second favorite writing application. One of my favorite features of Ulysses is the ability to theme the markdown writing. Here are a couple themes I threw together.
Ulysses is available on Mac and iPad. iA Writer is available on Mac, iOS, and Android.
This theme is monochromatic and influenced by iA Writer.