Hey Kris,
If you haven't see this, Nook Android:
I am strongly convinced a dropdown with the most used settings would be both simple and clear for the average user, plus make the most often used settings most quickly available. In this screenshot, themes are immediately identifiable, and a long press could be used to customize + reset to default. I might choose how ever many themes would fit in a row, plus a last icon that is either settings or a + to add more or place theme addition and re-ordering in ePub preferences, then the row becomes scrollable if there are more. Other less used settings could be an icon, that shows a detail screen in the popup, and perhaps other less used settings like # of columns, justify, hypenation, … moved to ePub settings. Advanced ePub settings could also be a gear icon in the same popup and then the other in-book menu limited to what aren't ePub settings, like share, open in (SxS, …), etc. Lock-orientation, I'm not sure, perhaps it's unneeded and one could rely on the control center.
Other issues relating to needed margins on all sides, it is difficult as well to activate notification center or control center without triggering brightness adjustment. If it's possible to have the gesture be hold a finger or thumb somewhere on the screen, and then use another to slide, that could work.
Plus, all settings screens could use a search, as with iOS Settings and OS X Sys Preferences. Perhaps iOS doesn't have any built-in method to implement search, but very possibly they later will.