From the Preface:
People in general, especially in this Age of Kali, are enamored by the external energy of Kṛṣṇa, and they wrongly think that by advancement of material comforts every man will be happy. They have no knowledge that the material or external nature is very strong, for everyone is strongly bound by the stringent laws of material nature. A living entity is happily the part and parcel of the Lord, and thus his natural function is to render immediate service to the Lord. By the spell of illusion one tries to be happy by serving his personal sense gratification in different forms which will never make him happy. Instead of satisfying his own personal material senses, he has to satisfy the senses of the Lord. That is the highest perfection of life. The Lord wants this, and He demands it. One has to understand this central point of Bhagavad-gītā. Our Kṛṣṇa consciousness movement is teaching the whole world this central point, and because we are not polluting the theme of Bhagavad-gītā As It Is, anyone seriously interested in deriving benefit by studying the Bhagavad-gītā must take help from the Kṛṣṇa consciousness movement for practical understanding of Bhagavad-gītā under the direct guidance of the Lord. We hope, therefore, that people will derive the greatest benefit by studying Bhagavad-gītā As It Is as we have presented it here, and if even one man becomes a pure devotee of the Lord, we shall consider our attempt a success.
A. C. Bhaktivedanta Swami
12 May 1971
Read the Book at Vedabase or Download the PDF here Bhagavad-gita_As_It_Is