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>
    <alllinks galcontinue="Bearer_of_the_Black_Book|41" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1" ns="0" title="Main Page" />
      <page pageid="13" ns="0" title="The Rift Wars" />
      <page pageid="14" ns="0" title="Lost Mine of Phandelver" />
      <page pageid="23" ns="0" title="Primeval Thule" />
      <page pageid="38" ns="0" title="Character Classes" />
      <page pageid="214" ns="0" title="Descent Into Avernus" />
      <page pageid="218" ns="0" title="Violet Awakeners" />
    </pages>
  </query>
</api>