Leonardo Antaris has written massive and excellent volumes on two of the major companies in the Spanish firearms industry, Star and Astra. Both of these companies made a wide range of military and commercial handguns, and Antaris' book cover everything. They include historical context for the guns, details on many competitors to Star and Astra products, detailed production records, and excellent explanations of the differences between variants.
The books are not cheap, but are absolutely worth the price for anyone interested in Spanish handguns. Once they sell out (and only a few hundred of each were printed), they will be gone forever - so get your copies now.