From publisher blurb:
The Behind the Spells pdf series continues with the protective shield spell! This series examines those spells from the SRD that are listed time and again on character sheets throughout gaming.
These are the spells which, if on your PC's class list, will be taken as soon as possible and include such quintessential favorites as magic missile and fireball. Each pdf in this series examines the spellcaster who created the spell, one or more of the spell's hidden capabilities, and possible variants for the spell.
Includes two shield variants!