What does it mean to be an observant Jew in the 21st century? The question sounds deceptively simple, but the answer takes more than 30 rabbis and nearly 1,000 pages in the massive volume being published later this month by the Rabbinical Assembly of Judaism’s Conservative movement, “The Observant Life: The Wisdom of Conservative Judaism for Contemporary Jews.” That’s nearly twice the length of the book it updates, Rabbi Isaac Klein’s 1979 “A Guide to Jewish Religious Practice.” Has the world — or Judaism — changed that much in the 33 years in between the appearance of those books?

What both volumes share is a firm grounding in Jewish religious law, known as halacha. That word comes from halach, the Hebrew word for “to walk” or “to go.” But the path the newer book sets out goes beyond the rituals and regulations detailed in Rabbi Klein’s guidebook. And that is why comparing the two isn’t really fair, says Rabbi Martin S. Cohen, senior editor of “The Observant Life”: because despite the overlap of some of their contents, the books’ goals diverge.

“The Observant Life,” says Cohen, “goes places where many contemporary Jews would be surprised to find there is an aspect of Jewish observance. It combines a code of law with a code of etiquette — and most of all, a code of behavior and conduct befitting someone who wishes to, in the words of the prophet Micah, “walk humbly with your God.”

Indeed, “The Observant Law” traverses far outside the walls of the synagogue to explore the challenging territory of ethics and morals of daily life. Reading it is like embarking on a journey into how to apply and translate into concrete, everyday behavior traditional Jewish values of “acting justly” and “deeds of lovingkindness.” Chapters thus confront such thorny areas as sex (including same-sex issues) and family life (such as intermarriage), as well as business issues (from negotiating fairly to the halacha of advertising to dealing with contracts that abrogate basic human rights) and the ever-more complex medical dilemmas with which modern medicine presents us (or will soon enough, with stem cells and cloning). Not to mention such current issues of concern as the environment. Modern technology is not below the radar, either: One entire chapter is devoted to intellectual property, touching on such issues as Internet file sharing, downloading and copying.

“These are all issues that the modern world has presented to us,” says Cohen. The ancient sages could not have anticipated them, he says. But there are insights from tradition that can help guide us in our thinking today.

The book — which took 10 years to compile — is a monumental undertaking. The list of more than 30 rabbis who contributed chapters reads like a contemporary greatest hits of Conservative Judaism, including Gordon Tucker, Elliot N. Dorff, Jane Kanarek, Nina Beth Cardin, David H. Lincoln, Cheryl Peretz, Jeremy Kalmanofsky, to name but a few. In some ways, it can be seen as a modern-day continuation of Maimonides and his codification of Jewish law and ethics. But there is hope, no doubt, that it will appeal to a new generation of observant Jews.

See, for instance, the chapter on being single in a sex-suffused culture. There’s no question, in the pages of this volume, that being observant is fully compatible with equality between men and women. The volume’s openness to confronting the fact that changes in the modern world challenge us to change further serves as a way to distinguish the Conservative movement from the other branch of Judaism based on traditional halacha, the slower-to-change Orthodox movement (which does not allow the rabbinic ordination of women, for instance) — as well as from those branches, such as the Reform and Reconstructionist, that have broken from strict adherence to halacha.

“The Observant Life” arrives at a pivotal moment for the Conservative movement, as it has lost adherents and is seen by skeptics as floundering, and lacking a vision. Is “The Observant Life” an attempt to address that perception? In her preface, Rabbi Julie Schonfeld, executive vice-president of the Rabbinical Assembly, puts it this way: “As the Conservative movement moves from the first to the second decade of the twenty-first century, we are reaching a turning-point in our approach. … This book is called ‘The Observant Life’ because we remain steadfast in belief that observing Judaism — that is, practicing mitzvoth — is the pathway to uncovering the full richness of Judaism in our lives.” The book reflects the fact, she continues, that the Conservative movement is “unequivocally committed to allowing thoughtful change in order to promote eternal values. … We embrace the realization that, if we are ‘commanded’ or obligated to perform the mitzvoth, that commitment applies to the ethical precepts as well as the ritual ones.”

“The Observant Life” also seems to point to (and derive from) larger trends within the Jewish community as a whole: a divergence of trends, really, with affiliated Jews becoming more observant, even while there are greater numbers of unaffiliated Jews who follow little or no observance. Those trends play out a bit differently in each of the movements, for somewhat different reasons. For instance: The past years have seen any number of Orthodox rabbinical rulings that further restrict foods acceptable to kashrut (from greens that might have microscopic bugs to certain kinds of fish). But particularly problematic is the reluctance if not refusal of the Orthodox movement to recognize Jewish conversions if not performed by an Orthodox rabbi.

Sociologists have suggested that one reason for reaching towards more extreme interpretations is not just competition (“I’m more observant than you”), but differentiation from the outside, secular world.

Meanwhile, the Reform movement, which from its beginnings eschewed many traditions and rituals, from keeping kosher to conducting services mostly in Hebrew and wearing yarmulkes and tallit — it bases its precepts not on halacha but on ethical ideals of social justice — now incorporates much more Hebrew, many of its rabbis and cantors wear yarmulkes and tallit, and several years ago it published a new prayer book that reflects the congregants’ desire for more connection and spirituality through ritual. So if “The Observant Life” is a reflection of the desire to figure out the “how to” of observance, it is of particular interest that one of the book’s publicity blurbs comes from Rabbi David Ellenson, president of the Hebrew Union College-Jewish Institute of Religion of the Reform movement.

Which brings us back to the Conservative movement, which is seen by many Jews as being in between the Reform and the Orthodox — to paraphrase like Goldilocks: not too strict, but not too secular. “The Observant Life” is one way to rebrand the movement for the public, to be seen and identified as a pathway towards a life that is religiously and spirituality committed while also living in the secular world (hence all those chapters about ethics in personal and business life). I think part of the value of “The Observant Life” is that it recognizes that the complications of modern life and culture and technology make it all the more perplexing to find ways to find a pathway that respects the push-pull of both spheres of life. It’s no small feat to interpret in a contemporary context ancient laws and rulings and tractates. But the rabbis take the task seriously, and I think not just Jews but anyone seeking to find a pathway towards just conduct would do well to dip into a volume whose heft is warranted by the value of its content.