Brahma Sutras systematizes the philosophy of the Upanishads in 555 aphorisms. In this book the original aphorisms are given in Devanagari followed by word-for-word English rendering, and the interpretation of the sutra according to Shankaracharya. The introduction contains a comparative study of the bhashyas of Shankara, Ramanuja, and Nimbarka.
After every happiness comes misery; they may be far apart or near. The more advanced the soul, the more quickly does one follow the other. What we want is neither happiness nor misery. Both make us forget our true nature; both are chains--one iron, one gold; behind both is the Atman, who knows neither happiness nor misery. These are states, and states must ever change; but the nature of the Atman is bliss, peace, unchanging. We have not to get it, we have it; only wash away the dross and see it.
-Swami Vivekananda