THE GATE BEHIND THE WALL by Samuel Heilman (Summit: $15.95). Heilman's is a wondrous book, a story of the quest for a soul. On sabbatical to Jerusalem, the author, a professor of sociology at Queens College, feels impelled to search out the depths of wisdom and revelation contained in the Talmud, that compilation of centuries of oral comments--and commentaries--on the Torah. His search takes him in and out of several Chavrusot, the intimate study circles in which pious Jews spend their entire lives--literally--delving into interpretations and meanings of biblical phrases. It's an endless quest, for "one can never know the Talmud," one can only be possessed by it. Surrounded by men of almost mystical qualities, Heilman studies and searches, wandering the dark alleys of Jerusalem's Mea Shearim quarter, until, toward the end, he finds a Chavrusah that meets his needs and that may eventually lead the trained scientist to inner peace. It's a disturbing experience, especially for someone trained in the world of rational knowledge. At the end Heilman is still the sociologist, but he has caught a glimpse of what is behind the wall of Jewish mysticism and Talmudic knowledge.