Guru tattva #12
Vaishnava culture as it relates to the books....
Here's another angle. Book distribution is an essential aspect of spreading the knowledge, and it's much more effective because there's too much information to convey in conversations. But book distribution in and of itself is not the sum and substance of 'spreading the mission'. It is only phase one of the mission, ie: get the knowledge into the hands of conditioned souls.
Phase two is to assist those who respond favorably to that knowledge and express a genuine eager interest in moving forward on that path. That is sadhu-sanga. Those who are serious and become devotees must then be guided by various gurus until they attain prema. Then the mission for that jiva is complete.