The discovery of the Dead Sea Scrolls brought to light the writings of an unknown community of sectarian Jews. Thomas (Religion, California Lutheran University) makes a careful linguistic study of the more esoteric of the texts, particularly following the use of the word raz, usually translated as "mystery". He is interested in the ways in which the authors, whom he believes to have been priestly scribes, the Yahad, used the "mystery" language to establish their own authority in terms of mystical, priestly language and the creation of a secret knowledge that set them apart. This informed their apocalyptic writings as well as their mystical desire to understand God. Much of the book is a detailed lexicology of the texts that traces the sources of the Yahad's beliefs as much as possible. This is a fine addition to serious Qumran studies. The Society of Biblical Literature publishes the paperbound edition; Brill publishes the hardbound. Annotation 2010 Book News, Inc., Portland, OR (booknews.com)