You are looking at the HTML representation of the XML format.
HTML is good for debugging, but is unsuitable for application use.
Specify the format parameter to change the output format.
To see the non HTML representation of the XML format, set format=xml.
See the complete documentation, or API help for more information. 
<?xml version="1.0"?>
<api>
  <query-continue>
    <allfileusages gafcontinue="Cover-13-Jess.jpg|4" />
  </query-continue>
  <query>
    <pages>
      <page pageid="4" ns="0" title="Hauptseite" />
      <page pageid="22" ns="0" title="Benjamin Walker" />
      <page pageid="23" ns="0" title="Coco" />
      <page pageid="43" ns="0" title="Band 1 „Die Suche beginnt“" />
      <page pageid="56" ns="0" title="Band 10 „Liebe vs. Vernunft“" />
      <page pageid="57" ns="0" title="Band 11 „Bruderkampf“" />
      <page pageid="58" ns="0" title="Band 12 „Die Erlösung“" />
    </pages>
  </query>
</api>