Dr. Beth M. Sheppard, a librarian at United Library at the Seabury-Western Theological Seminary has written an excellent essay on the bibliographic essay. She describes very clearly the differences and similarities among book reviews, annotated bibliographies, and articles. Her article is only 3 pages long and easy to read and understand. If you want a good grade for this assignment, it's imperative that you read this article and fully understand what you will be writing. After you have read the article, I would suggest you review some of the BEs I have linked for you under Examples. Below is the link to Dr. Sheppard's article:
http://journal.atla.com/ojs/index.php/theolib/article/viewFile/29/44
To synthesize Dr. Sheppard's article, the required elements of a bibliographic essay are:
In addition to Dr. Sheppard's recommendations, I would add these:
A bibliographic essay identifies and evaluates the core literature of a field of study. Like an annotated bibliography, it describes and analyses the sources, which can include books, book chapters, periodical articles, Web sites etc. In addition, it compares, contrasts, and evaluates the sources in relation to one another other. (Dr. Judith Freidenberg, http://www.lib.umd.edu/MCK/anth468Yspring2008.html)
A bibliographic essay is a critical essay in which the writer identifies and evaluates the core works of research within a discipline or sub-discipline. (http://www.ohiodominican.edu/library/quickref04/writing/biblio.pdf)