His Divine Grace A.C. Bhaktivedanta Swami Prabhupada would daily write letters to his disciples and important persons throughout the world.
He ran his international society mostly by letters.
By studying and reading these letters we can have tremendous insight into the practical workings of what Srila Prabhupada envisioned and instructed for his society, as well as gain personal realization by how he dealt with his disciples. for his fully self realized instructions were meant to be studied by the whole world for the next thousands of years.
Free Download scans of the original Prabhupada letter books