If you want a extremely simple way to convert several types of eBooks to ePub for the iPad you will want to try iiiConverter.
iiiConverter is a free online tool that allows users to convert various types of e-books, audio files and short video clips to the native media formats of Apple products: iPad, iPhone and iPod Touch. Output formats are: epub for e-books (*), m4a for audio and m4v for video.
The iPhone and iPod touch since they don’t have native support for e-books. You will need to install special software.
iiConverter will convert all of these formats to ePub; doc, fb2, html, lit, lrf, mobi, odt, pdb, pdf, prc, rtf, txt.
Go to iiiConverter to get started and follow these steps.
Here are some instructions to change your cover on iBooks.
iiiConverter is fast and simple but if you have a lot of eBooks you want to convert I recommend Calibre. Calibre is free software that you can download to your Mac or Pc and convert eBooks to several different formats including ePub.