Evaluating informational books and historical fiction in light of biographies

I've already discussed evaluating informational books and historical fiction, but biographies, although similar, have a few distinctions.  Although accuracy, organization, design, and style are important, the most important part of evaluation in biographies is the presence of documentable dialogue.  If a character speaks a line in a biography, it needs to be documented as to where it came from.  If is isn't documentable it means it is more historical fiction.  The biography should be objective and tell a good true story.