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="Catalogação_no_Koha" />
  </query-continue>
  <query>
    <pages>
      <page ns="0" title="Busca facetada (Apache-Discovery)" missing="" />
      <page ns="0" title="Buscar revista no R2B" missing="" />
      <page pageid="191" ns="0" title="BVT" />
      <page pageid="692" ns="0" title="Bibliotecas Digitais de Teses e Dissertações" />
      <page pageid="1286" ns="0" title="Bibliotecas que Utilizam o Koha no Brasil" />
      <page pageid="677" ns="0" title="CARTILHA SOAC/OCS" />
      <page pageid="1343" ns="0" title="CKAN" />
      <page pageid="710" ns="0" title="Cadastrar revista no R2B" />
      <page pageid="702" ns="0" title="Cadastrar usuário no R2B" />
      <page pageid="674" ns="0" title="Cartilhas/Guias" />
    </pages>
  </query>
</api>