But as to whether one really needs his own teacher or not generally, books can be the teacher. When one Tibetan lama was about to die, he said to his disciple, "Now you should no longer rely on a human teacher, but you should rely on books to be your teacher." I think that's very wise. Without investigation and without knowing a person properly you may hurriedly take someone as your guru or teacher, and there is too much involved in guru devotion or guru yoga. So it could land you in trouble. The thorough investigation of a teacher is very, very important.
— His Holiness The Dalai Lama, 365 Yoga by Julie Rappaport