Renaissance oil paintings can be found in museums across the world, but many of the manuscripts are so fragile they have never been displayed in public. The Royal Academy show reveals an unexpected gold mine: a series of manuscripts stunningly illustrated with plates painted in a gum-and-egg-white mixture, then colored with different pigments. They affirm and deepen the significance of northern Europe’s Renaissance. Within the illuminations’ detailed depictions of nature and human expression, the curators locate the germs of later artistic innovations, including landscape painting and miniature portraits.

Though many illuminated books were lavish and costly, intended to demonstrate their owner’s wealth and power, most were commissioned for use in moments of private prayer. That makes this show a wonderful change from most exhibits of Renaissance art, where crowds jostle for space in front of a single work. Masaccio’s altarpieces were intended to be seen by entire church congregations, but only one person at a time can gaze into each illumination. Viewers are drawn first to the tiny, eye-catching details in the foreground of each picture–a hand gesture or a face animated in conversation. Then the turrets of a distant fairy-tale castle or sheep grazing on a faraway hill draw the eye deeper and deeper into the story, offering a moment of peaceful, solitary contemplation.

These books blur the once distinct boundary between two worlds, depicting medieval stories in a lively, engaging Renaissance style. One of the finest examples is Jean de Meun’s “Le Roman de la Rose,” a classic tale of the pain and delight of unfulfilled desire. Its naturalistic style, replicated throughout the works in this show, is a rich successor to the two-dimensional medieval illuminations. Also on display are Lieven van Lathem’s stunning and innovative illustrations for “Secret des Secrets,” a book of advice purportedly given to Alexander the Great by Aristotle.

Unlike the leading lights of the Italian Renaissance, manuscript illuminators usually remained anonymous. They became known chiefly by the names of their courtly patrons: the extravagant dukes of Burgundy, in the east of France, as well as lords in England, Scotland, Germany, Spain and Portugal. Jan van Eyck probably started his career as a manuscript illuminator, bringing a sure eye for detail to his later paintings. And on some occasions, artists known primarily as oil painters were commissioned to paint a significant illumination within a series–like Rogier van der Weyden’s stunning frontispiece for Duke Philip of Burgundy’s “Chronicles of Hainault.”

Manuscript illumination died out in Europe at the end of the 15h century, a victim of the printed book and the handover of the duchy of Burgundy to the Spanish crown. But it went out with a wild flourish; some of the most breathtaking works date from the end of the era. In the “Brandenburg Prayer Book,” an extraordinary sweep of 41 miniatures, Simon Bening used light to heighten the drama with flickering torches and glowing skies. It is a fitting symbol of northern Europe’s long-overshadowed Renaissance, which is ripe for a reassessment. The Royal Academy provides a wonderfully rich and enlightening one.