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="El_cazador_del_desierto|86" />
  </query-continue>
  <query>
    <pages>
      <page pageid="20" ns="0" title="Resúmenes solicitados" />
      <page pageid="32" ns="0" title="Dulce Chacón Gutiérrez" />
      <page pageid="36" ns="0" title="El príncipe de la niebla" />
      <page pageid="40" ns="0" title="Don Quijote de La Mancha" />
      <page pageid="49" ns="0" title="El Dador" />
      <page pageid="63" ns="0" title="El Libro de los Abrazos" />
      <page pageid="65" ns="0" title="Un ladrón entre nosotros" />
      <page pageid="93" ns="0" title="La voz dormida" />
      <page pageid="209" ns="0" title="Marina" />
      <page pageid="220" ns="0" title="Campos de fresas" />
    </pages>
  </query>
</api>