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  PDF Files (Adobe Acrobat)This is the most common format for ebooks. Google Custom Search
  CHM FilesMany ebooks appear in CHM format.
To find out more about how to read a CHM file, click here.
  DOC Files (MS Word)Microsoft Word Files.
Sometimes you can find books in this format.
  RTF Files (Rich Text)Sometimes you might find books in this format.  
  TXT Files (Plain Text)When all else fails... try this.