Sleep Timer

"How do I get to the Sleep Timer on the iPhone?"
In Bookmobile 6.x and Book Mower 2.x, swipe up or down on the lower left side of the main screen.

In Bookmobile 5.x and Book Mower 1.x, double-tap the clock icon in the middle of the skip buttons.

"Can I customize the Sleep Timer defaults?"
Yes, there are a number of sleep timer preferences, found in the "star" tab.