There must have been many spiritual teachers before Shankaracharya also but their literature is not vailable. Perhaps their writings are somewhere hidden in past. Those texts are not in circulation in the present day society. Shankaracharya, besides writing commentaries on the three textsÂ Upanishads, the Brahma-Sutra and the Bhagwat Geeta, has also written many original spiritual texts. In the present times his literature is very popular and useful for a spiritual seeker. His writings are very lucid and easy to follow.
Besides the literature of Shankaracharya there is a wealth of spiritual literature available which is written by masters like Ramanujacharya, Madhwacharya, Nimbarkacharya, Ballabhacharya and others. They have their followers and disciples as well. Many sects have also come up originating from such masters. Seekers join any of the sects and become followers of a master depending upon their capability and inclinations. They continue the various spiritual practices and Sadhana prescribed by the master and achieve Self-unfoldment. The teachings of the various masters may appear to be different from each other but essentially lead to the same goal. There are some learned men who feel that these various teachers and their traditions are steps on the path of Self-unfoldment, one leading to the other. If a seeker does not get fanatically attached to one tradition and moves ahead with enthusiasm and motivation for achieving the ultimate goal, he moves step by step and realizes the Ultimate Truth.