{
"books" : {
"-KfwYdQClUK9ivglf-Jq" : {
  "-KfwYdQClUK9ivglf-Jr" : {
    "author" : "Rand",
    "description" : "something",
    "id" : "-KfwYdQClUK9ivglf-Jq",
    "title" : "sometitle"
   }
  },
    "-Kfly2F4T_ORCra5e01W" : {
      "-Kfly2F4T_ORCra5e01X" : {
    "author" : "Rand",
    "description" : "something",
    "id" : "-KfwYdQClUK9ivglf-Jq",
    "title" : "sometitle"
   }
  }
}

var booksController = function () {
function all(context) {
templates.get('books')
  .then(function (template) {
    var data = [];

    var booksRef = firebase.database().ref('books');
    booksRef.on('value', function (snapshot) {
      var a = snapshot.val();
      data.push(a);
      context.$element().html(template(data));
    });
  });
}

<ul>
{{#each this}}
{{#each this}}
{{#each this}}
<li>
<p id="{{id}}">Author: {{author}}</p>
<p>Title: {{title}}</p>
</li>
{{/each}}
{{/each}}
{{/each}}
</ul>