Speaking of high-quality interfaces, I have to turn to Stanza.
Stanza is loaded with extra bells and whistles: With a single tap, you can switch to white-text-on-black (for lower-light reading); you can manually set color schemes and page-turning sounds. There are so many design choices you could waste hours configuring and reconfiguring the look and feel of your e-books with Stanza. But if you get to the reading part, books are sorted by subject as well as author and title, and you can dig in: A dictionary is two taps away, and you can search within a book for a word or phrase. How wonderful that will be for researchers and students. In addition to all these features, there are more book resources available through Stanza — there are romance books from Harlequin, O’Reilly tech books, self-published books through Smashwords, bestsellers and new books via BooksonBoard and Fictionwise that cost any variety of prices. And it’s also got Project Gutenberg’s free books, as well as other free collections from Munseys (pulp fiction and classics) and Random House. Although the books I’ve looked at on Stanza have these awkward Web-style paragraph breaks, they do better than Eucalyptus in the illustration department. Stanza comes with a free version of “Alice’s Adventures in Wonderland” by Lewis Carroll, and the original illustrations look marvelous.
Stanza supports the industry standard epub format – See the Stanza FAQ on how to convert to epub format.