File upload using AngularJS and Rails

I have a model BOOK that will insert the book details through angularjs controller

Here is my view:

<h1 align="center">Books</h1>
<div ng-controller="BooksCtrl" class="container">
  <div class="row-fluid">
    <div class="col-md-6"> 
      <form ng-submit="addBook()" class="loginform cf">
        <input type="text" ng-model="newBook.title" placeholder="Title of the Book" required>
        <input type="text" ng-model="newBook.isbn" placeholder="ISBN Number of Book" required>
        <input type="file" ng-model="newBook.book_link">
        <input type="text" ng-model="newBook.edition" placeholder="Edition of the book" required>
        <input type="text" ng-model="newBook.publication_id" placeholder="Select the publication ID" required>
        <input type="submit" value="Add Book">
      </form>

      <div ng-show="editorEnabled" class="loginform cf">
        <form ng-submit="update()">
          <input type=text ng-model="editableBook.title" ng-show="editorEnabled" required>
          <input type=text ng-model="editableBook.body" ng-show="editorEnabled" required>
          <input type="submit" value="Update" class='btn'>
          <a href="#" ng-click="disableEditor()" class="btn">close</a>
        </form>
      </div>
      <div ng-show="selectedBook" class="loginform cf">
        <h2>{{selectedBook.title}}</h2>
        <p>{{selectedBook.body}}</p>
      </div>
    </div>

    <div class="col-md-6">
      <ul style="list-style-type: none;">
        <li ng-repeat="book in books" class="loginform cf" >
          <div>
            <div>{{book.title}}</div>
            <a href="">
              <img src="{{book.book_link.thumb.url}}"/>
            </a>


            <button href="#" ng-click="showBook(book)" class="btn">Show</button>
            <button href="#" ng-click="enableEditor(book)" class="btn">edit</button>
            <br>
          </div>
        </li>
      </ul>
    </div>

  </div>
</div>

My angularjs Controller function is:

book = Book.save($scope.newBook, function(data,headers) {
        console.log(book);
        $scope.books.push(book);
    }, function(data,headers) {
        // do the error case  
        console.log(data);
        if (data.status == 422)
        {
            alert("validation is failed book should be unique");
        }           
    });

The problem is that it is storing all the details except the book pdf upload. It is not passing even the name. How can I solve this? Any Suggestions would be appreciated.