R. Joseph ben Ephraim Karo (1488-1575) was born in Toledo, Spain but after the expulsion of the Jews his family moved to Turkey. He became a brilliant Jewish scholar, but, at the same time, became involved in Kabbalah. He met and was strongly influenced by Solomon Alkabetz. Together, they created the ritual of Tikkun Leil Shavuot, the tradition of staying up all night on Shavuot evening. It was during one of these all-night rituals, that R. Karo was visited for the first time by his maggid, an angel who perched on his shoulder and kissed Jewish law into his mouth. Inspired by this combination of mysticism and Halachah, R. Karo began writing his major work, the Beit Yosef in 1522. It took twenty years to complete. The Beit Yosef, written as a voluminous commentary to an earlier code, the Tur, was R. Karo's attempt to codify all of Jewish law. It was a huge undertaking because he tried to show the origins of all halakhic decisions in his code before arriving at each decisive ruling. He applied Talmud, Alfasi, Rambam's Mishneh Torah, R. Adret's responsa and a legion of other post-Tur legal decisions, demonstrating familiarity with all of the great legalists and included varying community customs. R. Karo then wrote a short digest of all of the laws he had dealt with so extensively in the Beit Yosef. Aimed as a simple guide for young students, this digest listed in concise Hebrew what a Jew was supposed to do in each circumstance of life. R. Karo tried to follow a formula for declaring what the Halachah was when previous sages were in disagreement, but, like Rambam, he created controversy by his decisions. He called his simple guide of legal decisions the Shulchan Arukh, the Prepared Table, because it made Halachah available to even the simplest Jew. R. Karo assumed that the scholarly reader who wanted the ocean of legal discussions would refer to the Beit Yosef. He therefore wrote the Shulchan Aruch in the same format as his more scholarly work. He divided it into easily-found sections and paragraphs. It's clear that he intended for his two works to be read together. Together with the commentary of R. Moses Isserles, who, added a commentary of Ashkenazic customs to the Shulhan Arukh it became the standard work on Jewish law to the present.

Hayyim dov Ber Friedberg (1876–1961 was born in Cracow, and in 1900 moved to Frankfort, where he worked for the publisher and bookseller Isaac Kauffmann. In 1904 he set up his own firm and by 1906 had published two catalogs; in the same year he and J. Saenger founded the publishing house of Saenger and Friedberg. In 1910 the partnership broke up, and Friedberg entered the diamond trade, moving to Antwerp. When the Nazis occupied Belgium, he lost his valuable library and all his papers. In 1946 he settled in Tel Aviv, continuing to deal in diamonds but with his heart in books and his bibliographical and genealogical researches. Beginning in 1896 Friedberg published in Hebrew a number of biographies, among them, in addition to this work, Shabbetai Kohen (1898), and Nathan Spira (1899); family histories, e.g., Schor (1901), Landau (1905), and Horowitz (1911, 19282); and a study on the old Jewish cemetery of Cracow, Luhot Zikkaron (1897, 19042, 1969). Friedberg's first bibliographical effort was a history of Hebrew printing in Cracow, Ha-Defus ha-Ivri be-Cracow (1900), followed by a similar study on Lublin, Le-Toledot ha-Defus ha-Ivri be-Lublin (1901). In 1932 he began publishing a series of works on the history of Hebrew printing, Toledot ha-Defus ha-Ivri; the series included volumes on Poland (1932, 19502); on Italy, Spain, Portugal, Turkey, and the Orient (1934, 19562); on Central Europe (1935); and on Western Europe (1937). His greatest achievement was his bibliographical lexicon Beit Eked Sefarim (1 vol., 1928–31; 4 vols., 1951–562, the second edition listing Hebrew books published by 1950). Friedberg's works are are indispensable bibliographical reference books.