Sefer Eshkol Ha-Kofer ("The Book of the Cluster of Henna Blossoms"), written by the Karaite Sage Judah ben Elia Hadassi the Mourner in Constantinople in the mid-twelfth century, is unique in the annals of Hebrew literature, in terms of both content and style. The book is a monumental composition which includes more than 350,000 words, consisting of approximately 400 rhymed acrostics. Eshkol H a-Kofer is devoted principally to legal discussions, organized according to the order of the Ten Commandments, and it analyzes all facets of Karaite religious life, usually presenting strict interpretations of the law. Included as well are numerous arguments against Rabbinic Judaism, theological, scientific and grammatical discussions, biblical exegesis, and much more. The book is a veritable treasure trove whose contents have been investigated by scholars of both Karaite and Rabbinic Judaism for much valuable information. It is a major source of knowledge of Karaism, but its importance for Rabbinic literature is also considerable. The only previous edition, completed 190 years ago, was quite deficient, censoring many passages and omitting almost all the Judaeo-Greek words and phrases that Hadassi used. A new edition, based on the best manuscripts, has long been a scholarly desideratum, and the present edition is intended to fill that need.