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="BHT50XL_4.jpg|1293" />
  </query-continue>
  <query>
    <pages>
      <page pageid="1235" ns="0" title="Bell and Howell 1227 XL" />
      <page pageid="1248" ns="0" title="Bell and Howell 2148" />
      <page pageid="1272" ns="0" title="Bell and Howell 492" />
      <page pageid="1284" ns="0" title="Bell and Howell MS 45" />
      <page pageid="1293" ns="0" title="Bell and Howell T 50 XL" />
      <page pageid="3775" ns="0" title="Bencini Comet P 122 Dual Projector" />
    </pages>
  </query>
</api>