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="Blood_at_the_Root.jpg|1571" />
  </query-continue>
  <query>
    <pages>
      <page pageid="139" ns="0" title="Becoming a Revolutionary" />
      <page pageid="221" ns="0" title="Beggars and Choosers" />
      <page pageid="222" ns="0" title="Black Chicago" />
      <page pageid="238" ns="0" title="Black Corona" />
      <page pageid="243" ns="0" title="Betty Friedan and the Making of “The Feminine Mystique”" />
      <page pageid="250" ns="0" title="Beyond Chinatown" />
      <page pageid="612" ns="0" title="Bad Girls Go Everywhere: The Life of Helen Gurley Brown, the Woman Behind Cosmopolitan Magazine" />
      <page pageid="654" ns="0" title="Black, White, and Indian" />
      <page pageid="2019" ns="0" title="Black Skin, White Masks" />
      <page pageid="5654" ns="0" title="The Mythical World of Nazi War Propaganda, 1939-1945" />
    </pages>
  </query>
</api>