Illuminated manuscripts are fascinating rarities, but typically we are allowed to see only a single two-page spread, entombed behind glass, as the books are certainly too precious to be handled by a mass public. But now, in a rare opportunity, the Morgan Library & Museum is presenting "Demons and Devotions: The Hours of Catherine of Cleves," an exhibition of nearly 100 pages from one of the finest 15th-century Dutch manuscripts (as it is unbound for conservation, copying and rebinding).

The illuminations are a joy to look at, brightly colored and lavishly gold-bedecked, minutely detailed and compositionally innovative. Through these images, we can experience the medieval world and also sense the first stirrings of the Renaissance and even 17th-century Dutch art.

The naturalistic renderings of people, interiors and objects, as in the charming Holy Family at Work, which incredibly shows the Christ child in a little wheeled baby walker made of wood, foreshadows the increasing secularization of a society dominated by the church. This manuscript was really at the tipping point between Gothic art grounded in religious contemplation and an increasingly secular culture.

Catherine of Cleves (1417-76), who spent much of her adult life in political struggle with her husband for control of their Rheinish duchy, commissioned her Book of Hours around 1440. Scholars believe it to be the work of a single, anonymous Dutch artist of exceptional talent (referred to as the Master of Catherine of Cleves), containing prayers for the hours of every day of the week, a suite of 57 petitions to individual saints, an unusually large number of illuminations (157 now, originally 168), and innovative borders, no two of which are alike.

The manuscript has a convoluted history. After dropping out of sight for 400 years, it resurfaced in the 19th century, when a bookseller split the work into two seemingly complete Books of Hours by shuffling the pages around. The Morgan bought the two parts (minus a few leaves that disappeared), one in 1963 and one in 1970.

Now the two manuscripts have been unbound, a deluxe facsimile edition made, and eventually the pages will be rebound into one book with the pages in their original order.

As a prayer book, a Book of Hours was designed to foster righteousness through empathy with the sufferings of Christ and allow penance for one’s transgressions. Rather than asking for one’s sins to be forgiven directly, entreaties were made to the Virgin Mary and other saints and martyrs that might intervene in saving the soul of the user. Catherine herself appears in the book several times, but never more to greater effect than at the beginning, where she is depicted kneeling before the Virgin.

In the opening illumination, Catherine of Cleves appears beseeching the Christ child through the intersession of the Virgin. With so many of her heraldic shields scattered about, the viewer wonders how much help she really needs. Her regal red gown spills out of the frame of the crowded page as if unstoppable, which draws attention to the figure. Despite the golden aureole around the standing Virgin, Catherine manages to call attention to herself, subtly upstaging the Virgin and Christ.

This image of Catherine looks back to the tiny figures of patrons inserted into the corners of panel paintings and other illuminations of the Gothic, but it also looks ahead to full-scale portraits of ordinary people rather than saints.

In the medieval world, a believer constantly assessed his or her state of grace in case of death, so that he or she would not end up swallowed by the Mouth of Hell, one of the most famous and surreal illuminations in this Book of Hours. The scene is frenzied and weird.

A feline mouth opens to expose another feline mouth with fire licking at bodies that are being forked into hell’s maw by devils. A devil pushes a wheelbarrow full of the dead into the scene, while towering chimneys form a gatehouse to hell that morphs into another feline head, this one with an open mouth spewing flames.

The Renaissance may have reveled in its own grotesques, but the medieval world’s fascination with eternal damnation really outdoes them. Catherine of Cleves’ hell is not as scatological as some by Hieronymous Bosch (ca. 1450-ca. 1516), who would take up the theme a little later, but hers is unnerving nonetheless.

Deathbed is as much a genre scene as a religious warning that all things pass. A dying man is attended by a doctor, who inspects a urine specimen, while various people pray at his bedside. Each object is shown in detail. A young man (perhaps a son or other relative) appears in the back of the room and again in the lower border, bending over a money chest from which he’s extracted a bag of loot. In many of the borders, the artist paints vignettes that comment upon the main image, such as the futility of the old man hoarding his money.

Although religious analogies were common in the 15th century, the Catherine of Cleves’ artist uses associations, both religious and not, in this unusual work. The Infant Christ Sent to Earth shows God the Father sending the dove of the Holy Trinity and the soon-to-be-mortal Christ child with his cross to earth. This is a fairly standard trope.

But in the lower border, the artist shows a fisherman putting fish into a basket with his other implements nearby, as ducks swim around. Is this meant as a symbolic illusion to Christ as the fisher of men? Or another of the more fanciful drolleries hidden in the borders? Whatever it is, the viewer gets a very close look at what fishing was like in the 1440s.

Besides the main series of prayers and hymns, one optional part of Books of Hours was a section of suffrages, or prayers to specific saints. The freedom to include whatever saints the owner wanted (and could afford to have illustrated) really fired the imagination the Master of the Hours of Catherine of Cleves.

The saints here usually stand holding an identifying attribute in rather simple compositions, but there is compensation for that simplicity in the creative flights in the borders. Saints Cornelius and Cyprian are surrounded by all sorts of contraptions that turn out to be birdcages. St. Vincent is surrounded by butterflies, and St. Lawrence is edged in fish eating other fish plus entwined eels!

St. Lawrence was martyred on a grill, hence the fish? Did Saint Cornelius being the patron saint of pets inspire the birdcages, or did Catherine just like birds? The excitement in these images seems to me to go beyond whatever religious significance they may or may not have had.

The individual mind was at play and soon the artist would be even freer.

N.F. Karlins is a New York art historian and critic.