okular/x-mobipocket-ebook.xml

<?xml version="1.0" encoding="UTF-8"?>
<mime-info xmlns="http://www.freedesktop.org/standards/shared-mime-info">
  <mime-type type="application/x-mobipocket-ebook">
    <comment>E-book in Mobipocket format</comment>
    <glob pattern="*.mobi"/>
    <glob pattern="*.prc" />
    <magic>
        <match type="string" offset="60" value="TEXtREAd" />
        <match type="string" offset="60" value="BOOKMOBI" />
    </magic>
  </mime-type>
</mime-info>