I don't want to sign up, can I check out how things look with my cellular phone?

Sure, there's mobile book reading demo just for that. Note that image mode is used with demo mode -- that is, book pages are shown as images, not plain text. This allows for more effective page layout with most cell phones, since the mobile device's screen is usually shaped as a vertical rectangle.

For more information about different display modes, see this FAQ article: Displaying mobile ebooks