AFAIK the Kindle App for iPhone will read regular Mobi files (which is basically what most Kindle files are). Calibre will convert ePub's to Mobi as long as they aren't DRM'd. If it's DRM'd you'll need to use Inept on it first to remove the DRM.
"The test of any good fiction is that you should care something for the characters; the good to succeed, the bad to fail. The trouble with most fiction is that you want them all to land in hell together, as quickly as possible."
— Mark Twain