File upload using AngularJS and Rails - ruby-on-rails

Question

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'>
close
</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.