ActiveRecord::HasManyThroughSourceAssociationNotFoundError in ReadingsController#index
Could not find the source association(s) :reading or :readings in model UserBook. Try 'has_many :readings, :through => :user_books, :source => <name>'. Is it one of :user or :book?

Extracted source (around line #5):
    @book = Book.new
    @reading = Reading.new
    @readings = current_user.readings.newest_first
  end