I used Scrivener's desktop app to help me package my first book five years ago. Today, I write most of everything on my phone. For that, I use a combination of tools like ByWord, iA Writer, and Evernote which all sync to the cloud. I also signed up to PressBooks to package my latest book. It functions just like WordPress.
Scrivener is late to the mobile game. Based on the screenshots, it looks like the exact same flow as the computer version. If you're a serious writer, especially one that writes novels and screenplays, it's worth giving this app a shot. It's available in the app store now for $19.99. Here's the full demo.