title_body: Paperwhite error on open book, how do I get the error log?
upvoted_answer: I don't think they make an app for the PaperWhite since it would appear it is Amazon content dedicated and not based of Android because I recall being able to install error logging apps from Android on my Kindle.  
  
  Since this is a DRM free book I would omit the usage of Calibre.  That said I would download Kindle Previewer and browse the book for any possibly display issues and see if you can duplicate the error.  
  
  If you have found no display issues or get any errors when viewing the book through Kindle Previewer I would install KindleGen and unpack the .mobi file back to .epub format.  Then run the .epub file through IDPF validation.  If you want you could edit the .epub file in Calibre but I would do it manually, that's just me, and then you can use KindleGen to convert back to .mobi format.
  
  If you find any issues and have paid for the book I would contact the buyer and inform them you have an issue with the .mobi file and would like a refund if you cant correct the issue.