The pre-Roman Era glass beads in the Archaeological Museum of Ibiza and Formentera. Not gorgeously illustrated, but with a serious text written by a trained archaeologist (i.e. including chemical analysis of the glass used in single beads).101 pages. With a short but interesting bibliography.
ISBN 84-87143-17-2
I was elated to learn there that men's necklaces were then short, while women's were long -- a fashion not yet obsolete, as most of the boys I see wearing necklaces do use chokers.