Obviously, this 47-page book isn't new, but it looks like a well-written resource AND it is available online (for free) in full-text! The online edition is version 2.1, but is not dated.
Introduction to Metadata: Pathways to Digital Information
By Tony Gill, Anne Gilliland-Swetland, and Murtha Baca
Published by the Getty Research Institute
http://www.getty.edu/research/conducting_research/standards/intrometadata/pdf.html (v. 2.1)
Technorati Tag: Metadata