There are a few ways that you can navigate chapters in the app! One is to enlarge the player by tapping on it and swiping the book cover back and forth to go forward or backward in the book.
Otherwise, you can select the chapter you’d like to listen to by going to the chapter lists. If you’re playing the book you can find this list by swiping up in the enlarged player to reveal an area where you can see all chapters.
The second way to find the chapter list is by going to the book info page by tapping on the cover in your Library.
If you’d like to start the book over, select the first chapter and be on your way!