AngularJS $save form data in a separate hash

Using this setup I can save a form in AngularJS.

I want to have the data values pushed to the server (via the $save method) as defined in the name="" attributes.

So a form submitted like this would look like this:

Ideal Form Data

{
  book: {
    word : '...',
    book : '...',
    page : '...'
  }
}

But instead its being submitted directly as a hash (without the inner book block).

Here's what my form and controller looks like:

My Form

<div>
  <form data-ng-submit="save()">
    <ol class="fields">
      <li>
        <div class="label">
          <label for="word">Word: </label>
        </div>
        <div class="details">
          <input type="text" name="word[word]" data-ng-model="word.word" />
        </div>
      </li>
      <li>
        <div class="label">
          <label for="book">book: </label>
        </div>
        <div class="details">
          <input type="text" name="word[book]" data-ng-model="word.book" />
        </div>
      </li>
      <li>
        <div class="label">
          <label for="page">page: </label>
        </div>
        <div class="details">
          <input type="text" name="word[page]" data-ng-model="word.page" />
        </div>
      </li>
    </ol>
    <nav class="actions">
      <input type="submit" value="save" />
    </nav>
  </form>
</div>

My Controller (Angular)

var saveCtrl = function($scope, $routeParams, Word, $location) {
  $scope.word = Word.get({
    id : $routeParams.id 
  });
  $scope.save = function() {
    $scope.word.$save({
      id : $scope.word.id
    });
    $location.path('/').replace();
  };
}

Any ideas?