Originally Posted by OverHaze
For instance books I purchased from the Humble Book Bundle look terrible on the Kobo Glo because I can't alter the margins.
Are they epubs? If so that is probably a problem with those particular books, e.g., if epub has a paragraph style that sets the margins, then this will override whatever margins you set in the Kobo options. This cuts both ways - if you could not override the Kobo options in the epub, then a lot of people would complain even more (including me).