title_body: How can I left justify text on my Kindle?
upvoted_answer: The justification is normally specified in the CSS included in your ebook. 
  Commercial ebooks often come 'justified', just like most traditional books (which generate less of a problem of large white space, through the combination of hyphenation and wider lines).
  
  It might be that the Kindle overrides the ebooks default, but I doubt it. What you should try is change the CSS in an ebook, e.g. by convert the ebook with Calibre, while specifying Text Justification: Left Alignin the Look &amp; Feel tab of the book conversion page.