books_controller.rb

class BooksController < ApplicationController
  before_filter :authenticate_user!

  def index
    @books = current_user.books
  end

  def new
    @book = Book.new
  end

  def create
    @book = current_user.books.build(book_params)
    if @book.save
      redirect_to root_path, notice: "Book created"
    else
      render :new
    end
  end

  private
  def book_params
    params.require(:book).permit(:title)
  end
end