BOOKS may appear to inhabit a flat, monochromatic space. But Sarah Werner, a director at the Folger Shakespeare Library in Washington, DC, stresses that they carry a wealth of information which pours out only on close inspection, by looking, touching or even smelling a physical copy. They also change over time. This richness cannot—at least not yet—be captured in book-scanning projects.

At the moment, these focus on the quantity of titles. This is understandable—and it makes sense. Most mass-produced editions from the 1800s to early 1900s (when copyright protection ends in many countries) tend to be indistinguishable. Scanning one copy is as good as scanning any other. But Dr Werner has long argued that older books are different. Printed in smaller quantities, each physical copy has unique properties. Dr Werner carefully opens a printed in 1631 edition of Christopher Marlowe's "Doctor Faustus" in a conference room at the Folger's building, adjacent to the Library of Congress. She turns to a page with a handprint on it. The stain had to be that of a printer's devil, as a young shop assistant was known in those days. The handprint extends into the binding (see picture), so it must have been made before the book was still in large sheets (called signatures) and before it was folded and bound, she explains. In "Incipit textus Sententiarum", a book printed in Basel in 1482, she shows your correspondent a similar handprint on an outer margin. That was probably smeared at a later stage, possibly by a reader. In a 1691 volume of often earthy poems by John Wilmot, Earl of Rochester, Dr Werner notes how several pages were cut out and replaced, and that there is a gap in folios, or page numbers, before a play appears at the end. The play is printed on slightly different paper, too. Dr Werner compared a Google Books scan to one of the replaced pages in the Folger copy, and found that two verses (more blatantly erotic than the rest of the ode of which the page is part) were added at the end of the poem. Such titbits are invaluable to scholars. Dr Werner points out the laid lines and chain lines, artefacts of paper-making, which indicate the orientation of the paper in the frame in which it dried. Wilmot's book has a section in the play where, curiously, the lines on the paper across several signatures are perpendicular to the rest of the book. (Cheaper paper cut to the wrong size? An error? Signatures left over from an unpopular printing of a play that was appended to more popular poems?)

The assembly is important. Previous centuries treated books and manuscripts interchangeably, Dr Werner says, and some books were delivered as loose pages that were folded, sewn and bound. Books had their covers and bindings removed at times, and were rebound into new forms that suited the owner. Dr Werner picks up a collection assembled from ten French and Latin works from 1575 of slightly different sizes, then another, a minuscule dos-à-dos, or back-to-back volume containing parts of the Old Testament, New Testament and Psalms (from 1626, 1630 and 1632, respectively) and used as a prompt during church services. Meanwhile, dirt and wear can shed light on how the book was read, while its aroma offers a hint of the compounds used to prepare paper to accept ink, and thus of the printing technologies used. A digital scan would mask many interesting differences in the patchwork edition.

Thanks to higher-resolution scanning, detail down to the grain of the paper can be captured, albeit at present this entails considerable costs. Three-dimensional scans are becoming routine and will soon be good enough to show cut pages, emendations, layers of ink and even details of the paper. Dr Werner appreciates such efforts, as well as the more humdrum ones by Google, ProQuest, Cengage Learning, the British Library, France's Bibliothèque Nationale and others (including the Folger's own). These have allowed many more academics to study many important aspects of books, not least their text, without damaging fragile copies. It is also helping safeguard their contents for posterity. But she worries that in the headlong march to preserve only books' words, people may lose sight of their less obvious attributes. They, she says, speak volumes, too.