From the Preface:

Christmas is one of the great days of obligation and observance in the Church of which I am a Priest; but it is much more than that, it is one of the great days of obligation and observance in the world. Furthermore it is one of the evidences of the power of Him Whose birth we commemorate that its observation is not limited by conditions of race and creed. Those who fail to see in Him what we see nevertheless see something and even by imperfect visions are moved to joy. The world transmutes that joy into blessing, not merely by giving of its substance but of its soul because men perceive that it is for the soul's good and because they hope to receive its benefits although they well know that giving is far better than receiving, in the very words of Him Who gave us the greatest of all gifts-Himself.