But... I don't see the advantage of having a touch screen for ebooks. I only ever want the next or previous page. Yes, a touch screen is perhaps more natural _when compared to a paper book_, but hitting a button for the next page means I don't obscure the screen with my fingers, and it's more comfortable to press (less movement).
- go to the table of contents
- click a hyperlink to another chapter
- open a search panel to search for text
Most will be used more when reading reference works then when reading literature, but a search can be useful in literature, too:
- if you want to make a quotation, it makes it easier to find the exact text to quote.
- if, on page 400 of the lord of the rings, you encounter a name that you vaguely remember, searching makes it easier to find out where the person or place was introduced.
Of course the UI can be designed for hardware buttons but at a certain point you're going to have to strike a balance between device size and user friendliness. For example, you could either: not allow text input, have a hardware keyboard, have a software keyboard navigated with minimal hardware buttons, or have a software keyboard with a touch screen. Of those I prefer a touch screen - the device will be smaller and/or have a larger screen and still be user friendly.