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="Kissyman_Era" />
  </query-continue>
  <query>
    <pages>
      <page pageid="549" ns="10" title="Template:Book" />
      <page pageid="550" ns="10" title="Template:Character" />
      <page pageid="1901" ns="10" title="Template:Crypt Era" />
      <page pageid="1927" ns="10" title="Template:Dystopia Triptych Stories" />
      <page pageid="551" ns="10" title="Template:Expand" />
      <page pageid="1902" ns="10" title="Template:GFL Era" />
      <page pageid="1955" ns="10" title="Template:GFL Novels" />
      <page pageid="1862" ns="10" title="Template:Gaming Modules" />
      <page pageid="1903" ns="10" title="Template:Generations Era" />
      <page pageid="1904" ns="10" title="Template:Hunter Hunterson Stories" />
    </pages>
  </query>
</api>