Missing Template Rails on Update

I have a jQuery script that looks like:

$.ajax({
  url: "/books/"+ mId,
  type: 'PUT',
  dataType: 'json',
  data: { book: { description: bValue } },
}).done(function() {
  alert("DONE!");
});

In my routes, I have resources :books

In my book controller, I have the following:

def update
  @book = Book.find params[:id]
  respond_to do |format|
    if @book.update(book_params)
      format.json { render status: 200 }
    else
      format.json { render status: :unprocessable_entity }
    end
  end
end

But for some reason, I get the following error:

ActionView::MissingTemplate (Missing template books/update, application/update with {:locale=>[:en], :formats=>[:json], :variants=>[], :handlers=>[:erb, :builder, :raw, :ruby, :coffee, :jbuilder]}.