''La Regenta'' is a bold Spanish novel that was first published in 1855. The author Leopoldo Alas (1852-1901) was a widely hated literary critic. When ''La Regenta'' appeared in print, it was attacked as obscene, irreligious, and a plagiarism of Flaubert's ''Madame Bovary.'' Such charges were baseless, but Alas had made too many important enemies for that to matter. ''La Regenta'' was soon forgotten. In the past 30 years, however, a growing body of critical opinion has come to regard ''La Regenta'' as a minor masterpiece. The story centers on the interaction between el magistral (a husband) - ''the man who is the master'' - and la regenta (the wife) - ''the woman who rules.'' The story portrays an intelligent, sensitive woman's quest for fulfillment through marriage, infidelity, and faith. Alas does not conceal his satirical wit, nor his sarcasm at the conventions of his times. What emerges is a masterful psychological study of marriage, rendered in the then-advanced techniques of realism. Translator John Rutherford provides an indispensable introduction.