Jewish prayer books have historically evolved across time and geography, challenging the notion that liturgical change violates Jewish law. A systematic halakhic analysis of Siddur Sim Shalom—the Conservative movement's first comprehensive prayer book—reveals both justified innovations and concerning departures from traditional Jewish law. By examining the siddur's Hebrew text, translations, and instructions against the Babylonian Talmud, rabbinic literature, standard codes, and historical liturgical precedents, this research identifies multiple areas where the prayer book successfully modernizes while maintaining halakhic integrity. These include thoughtful textual corrections, alternative prayer formulations, and updated liturgical passages. However, several elements prove problematic: English translations that alter required blessing formulations, instructions that may not fulfill halakhic obligations, and layout issues that impede comprehension. While change within halakhic parameters remains both permissible and sometimes necessary, Siddur Sim Shalom occasionally prioritizes innovation over tradition inappropriately. Despite the siddur's significant contributions to Conservative Jewish liturgy, the analysis recommends comprehensive review by the Law Committee to address these halakhic concerns.