OWL @ Purdue has a great site about how to write an Annotated Bibliography
A bibliography is a list of sources (books, journals, Web sites, periodicals, etc.) one has used for researching a topic. Bibliographies are sometimes called "References" or "Works Cited" depending on the style format you are using. A bibliography usually just includes the bibliographic information (i.e., the author, title, publisher, etc.).
An annotation is a summary and/or evaluation. Therefore, an annotated bibliography includes a summary and/or evaluation of each of the sources. Depending on your project or the assignment, your annotations may do one or more of the following.
Elements of a good Annotated Bibliography:
1) Bibliography according to the appropriate citation style (MLA, APA, CBE/CSE, etc.).
2) Explanation of main points and/or purpose of the work—basically, its thesis—which shows among other things that you have read and thoroughly understand the source.
3) Verification or critique of the authority or qualifications of the author.
4) Comments on the worth, effectiveness, and usefulness of the work in terms of both the topic being researched and/or your own research project.
Source: UNC Writing Center - Annotated Bibliography
