Eucalyptus is the best ebook reader for iPhone I’ve seen. Worth it for little more than the cost of a paperback (ten bucks). The pinching to zoom out is priceless and the comfort of the book management beats Kindle for iPhone hands down. The page turning beats Stanza. (And I don’t miss Stanza’s annoying, fake page turning sound.) And the book selection beats Classics, though I think Classics is still a pretty nice and unique offering.
The Eucalyptus developers got my ten bucks on the strength of the above review alone and I consider it money well spent. As implied above, I already use Kindle for iPhone, Stanza, Classics and, now, Eucalyptus.