Book excerpt: "Principles of Molecular Virology, Fourth Edition" provides an essential introduction to modern virology in a clear and concise manner. It is a highly enjoyable and readable text with numerous illustrations that enhance the reader's understanding of important principles. It contains new material on virus structure, virus evolution, zoonoses, bushmeat, SARS and bioterrorism. The standard version includes a CD-ROM with Flash animations, virtual interactive tutorials and experiments, self-assessment questions, useful online resources, along with the glossary, classification of subcellular infectious agents and history of virology.