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>
    <alltransclusions gatcontinue="Succession_box" />
  </query-continue>
  <query>
    <pages>
      <page ns="10" title="Template:Cite book" missing="" />
      <page ns="10" title="Template:Cite web" missing="" />
      <page ns="10" title="Template:End box" missing="" />
      <page ns="10" title="Template:F1" missing="" />
      <page ns="10" title="Template:Former F1 driver" missing="" />
      <page ns="10" title="Template:Lang" missing="" />
      <page ns="10" title="Template:Le Mans drivers" missing="" />
      <page ns="10" title="Template:Reflist" missing="" />
      <page ns="10" title="Template:S-sports" missing="" />
      <page ns="10" title="Template:Start box" missing="" />
    </pages>
  </query>
</api>