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>
    <allpages apcontinue="Battle_of_Haibi_Chapter_18" />
  </query-continue>
  <query>
    <allpages>
      <p pageid="1548" ns="0" title="Battle of Haibi" />
      <p pageid="1549" ns="0" title="Battle of Haibi Chapter 1" />
      <p pageid="1558" ns="0" title="Battle of Haibi Chapter 10" />
      <p pageid="1559" ns="0" title="Battle of Haibi Chapter 11" />
      <p pageid="1560" ns="0" title="Battle of Haibi Chapter 12" />
      <p pageid="1562" ns="0" title="Battle of Haibi Chapter 13" />
      <p pageid="1561" ns="0" title="Battle of Haibi Chapter 14" />
      <p pageid="1563" ns="0" title="Battle of Haibi Chapter 15" />
      <p pageid="1564" ns="0" title="Battle of Haibi Chapter 16" />
      <p pageid="1565" ns="0" title="Battle of Haibi Chapter 17" />
    </allpages>
  </query>
</api>