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 alcontinue="Data_source|11298" />
  </query-continue>
  <query>
    <alllinks>
      <l ns="0" title="Bayesian Methods for Hackers" />
      <l ns="0" title="Booklist: Python programming language" />
      <l ns="0" title="Booklist: R programming language" />
      <l ns="0" title="Booklist: artificial intelligence" />
      <l ns="0" title="Booklist: machine learning" />
      <l ns="0" title="Booklist: numerical analysis" />
      <l ns="0" title="Booklist: optimization" />
      <l ns="0" title="Booklist: probability and statistics" />
      <l ns="0" title="Booklist: probability and statistics" />
      <l ns="0" title="Booklist: software development" />
    </alllinks>
  </query>
</api>