Once Treharne realized that the French devotional had only recently been taken apart, she immediately logged into eBay, the most popular online marketplace for manuscript fragments. Before long, she had found a full-page illustration identical to one in the photographs on the Christie’s page. It was, without a doubt, a piece of her book. Soon, she found more leaves, each identified by the same seller’s inventory number, A263. It was a Leipzig-based dealer operating under the name “International Antique Art Gallery.”

In a panic, Treharne bought two bifolia—pairs of connected leaves—from the book’s liturgical calendar, as well as an illustrated leaf, in the hopes that she might reconstruct the manuscript, at least in part. As soon as she purchased these leaves, more appeared from the same Leipzig outfit. With prices ranging from a hundred and fifty dollars for a single leaf to twenty-three hundred for a miniature, Treharne realized that her reconstructive instinct would bankrupt her. After blogging about her experience and talking with colleagues, she concluded, “I will never buy another fragment.” Doing so, she now argues, only supports the market for broken leaves. (Recently, she noticed that some of the book’s leaves—which had been removed from eBay by the seller—were again available for purchase.)

Not all individual fragments are the products of books as opulent and complete as Treharne’s appears to have been. De Hamel told me in an e-mail that, by his estimate, ninety-nine per cent of today’s dispersed leaves belonged to books that were already “seriously defective” decades ago. A complete manuscript in pristine condition, he said, “is almost never broken up.” Yet it is perfectly legal to break books no matter how complete or rare they are, and it does still happen, particularly in the online, after-auction market. Sometimes it happens to books of considerable scholarly interest, as in the case of a liturgical calendar that David Gura, a curator at the University of Notre Dame, noticed on eBay, in 2012. From the listing, he could see that the cluster of pages came from a book of hours made in Brittany, where few manuscripts are known to have originated. Afraid that the complete calendar—twelve leaves in total—would soon be purchased, split, and sold separately (such secondary and tertiary breaking among dealers is not uncommon), Gura bought it.

“Usually we do not buy single leaves,” he said, referring to a Notre Dame policy shared by many institutions. “In this case, it was a very, very rare calendar, and it was in an effort to keep it from being further dispersed.”

By examining the calendar up close, Gura was able to trace it to a manuscript from the well-known Bergendal collection, parts of which were sold by Sotheby’s, in 2011. The calendar was part of Bergendal manuscript number eight—described by the auction house as complete save for three missing leaves. After locating more leaves online, Gura discovered that other features of the book—specifically its combination of prayers and saints’ days—made it an especially rare find even among existing Breton prayerbooks. Only by looking at different sections side by side did Gura recognize its rarity. If the sections were permanently separated, the book’s full import would be lost on future scholars.

Over the next year, Gura attempted to reconstruct the entire Bergendal manuscript as Sotheby’s had sold it. First, he contacted the dealer who sold him the calendar. Then, he reached out to other people who had bought leaves on eBay and urged them to sell their recent purchases to Notre Dame. (EBay has since made bidder names anonymous; his approach would not work today.) Through a combination of eBay contacts, offline dealers, and auction catalogues, Notre Dame has found and purchased ninety-one of the hundred and twenty-eight leaves that had been bound together at the time of the manuscript’s auction at Sotheby’s, including twenty-one of the thirty full-page illustrations. And Gura’s “salvage work” continues: he recovered five leaves in November.

Gura declined to identify any of the dealers he worked with, in part because antiquarian bookselling is a small world, and librarians who hope to recover broken manuscripts must maintain good relationships. But another reason that many experts refuse to point fingers is that those who sell recently unbound leaves are not necessarily the people doing the book-breaking. A dealer can always claim to have received the leaves in their present condition, or to simply not remember their provenance. (Nicholas Schmidle recently wrote in the magazine about the separate, but related, issue of rare-book forgeries.) Considering the anonymity of many transactions in the art world, there’s no way to be certain where in the process a manuscript has been broken—unless the dealer tells you outright.

Treharne was wary of contacting the Leipzig-based dealership that was selling so many leaves from the French manuscript, though she knew from the eBay account that the owner was a woman named Chidsanucha Walter. When I telephoned and wrote to the address listed on eBay, I received a response from a man named Thomas Walter. A legal professional, he told me that his wife owns the gallery and that he helps run it. In response to my questions about Treharne’s book, Walter sent me a friendly, if daunting, three-thousand-word e-mail in German, in which he detailed his philosophy of bookselling.

The preservation of truly rare books, he argued, is guaranteed by the prices they command. “In my experience, free-market forces in themselves lead to regulation,” he wrote, explaining that the most rare and sumptuous manuscripts are snapped up at auction by museums and large art dealers. The manuscripts that are left to small dealers like him are, by virtue of their availability, less valuable as complete relics. “That which is considered to be not as collectable or worthy of exhibition will, under certain circumstances, be taken apart,” he wrote.

As for the French devotional that ended up in Treharne’s hands, he said that he bought it from Christie’s, in 2010. The book may have been passed over by others at the auction, he said, because the binding had been replaced in the nineteenth-century, and some of the borders and miniatures were cropped in the process.

“This object was not attractive enough for the big dealers and museums,” he wrote, “all of whom could see its auction listing, and who left it to others to purchase.”

“Looking back,” he wrote elsewhere in the e-mail, “I can say that maybe not every book that I split into individual parts should have been split, but it’s an ongoing process of understanding. I try to acquire and sell all of my works whole, but for some objects, it’s clear from the start that they must be split.”

When I asked Walter about Treharne’s specific criticisms, he responded that he has helped create a wider audience for book art by enabling anyone to participate through eBay. “These works of art are now no longer reserved for only an élite group of people (dealers, museums and the rich),” he wrote.

Since the eBay boom in the early aughts, prices for manuscript leaves have stagnated, according to the Danish art scholar Erik Drigsdahl, leaving small dealers under increased pressure to sell more pieces at lower prices. Top-quality leaves are typically sold either at auction or by a small number of major galleries, all of which have trained art historians on staff. Sandra Hindman, who is both an art dealer and professor emerita of art history at Northwestern University—and who owns galleries in Chicago, New York, and Paris—told me that she is one of only a few dealers worldwide who trade at the “highest level” of medieval manuscripts, where individual leaves are sold only after an attempt has been made to thoroughly reconstruct their provenance. But with many leaves of uncertain origin already on the market, there will always be the temptation for some dealers to break apart books.