Medievalist and art-critic Mullins has published historical novels in England; this fictionalized look st Flemish painter Jan van Eyck is a competent but not very auspicious American debut. Van Eyck, remembered for his Ghent altarpiece, was court painter to the 15th-century Philip, Duke of Burgundy. Mullins' conceit--and it's a good one--is that Philip, recognizing van Eyck's penetrating psychological eye and the tendency of people to confide in him while being painted, used him as a sort of spy. As van Eyck executes portraits of the doomed Jacqueline, Duchess of Brabant (who led her own troops in battle, struggling to preserve her Netherlands inheritance from Philip), and Joan of Arc (captive of Philip, who is under pressure to turn her over to the English for trial), he becomes unwillingly embroiled in politics--and grows to hate the patron he once revered as the most civilized of men. But there's not much action in any of this, which would matter less if the characters were more fully realized. There's a background of Flemish merrymaking and civil unrest, as the merchant and artisan classes overwhelm the old culture of chivalry, and a subplot in which van Eyck wins the love of the innocent Margarethe but briefly loses her to a convent after an attempted rape by soldiers. Solid, interesting material, but a bit pat and static as fiction.