The book, its pages dense with Latin, was printed in 1573. Frank Mowery pauses a moment from sewing it back together and pulls a piece of ivory from the clutter on his workbench. It's as long as his index finger and flatter.

"This is the bookbinder's basic tool," he says. "It's called a bone folder, because most are made from goat bone. So this one's a little special. My professor gave this to me. His professor had given it to him."

Mowery's professor lives in Hamburg, Germany, and is now in his declining years. Frank Mowery, age 25, finds his star already well ascended. He is the binder and conservator at the Folger Library, which houses one of the finest collections of early English language books in the world. Ten years ago Mowery began binding books after school and during vacations for his father, who was the librarian at Ohio's Wittenberg University. The work soon claimed him. He wanted to be a "fine" book-binder, an artist as well as a craftsman. "In America, binding has never really been more than a trade. There was no place I could go where someone would take the time to teach me; and teach me well."

So his father, through book-dealer friends, made transatlantic inquiries. The name of a professor in Hamburg, Kurt Londenberg, came up. But Londenberg was old; he hadn't taught in five years. More to the point, he was considered the greatest living German binder. What interest would he possibly have in teaching a kid from Ohio?

Mowery wrote him a letter, stating his credentials. Londenberg answered within a week. "I, of course, was unknown to him. He told me that after the war he had nothing. The Marshall Plan had helped him out, and he wanted to repay the United States in some small way. He also told me that he had never taught someone from beginning to end and wanted to do that before he died."

Mowery left home at 17 and spent four and half years as Londenberg's sole pupil. "On the first day my professor brought in a stack of unbound texts for me to sew. He said it was up to me how much I wanted to learn, how much time I wanted to put in."

Mowery put in 12-hour days sewing those texts. He learned how to make, design, and conserve paper. He learned how to work with leather. He studied typography and art history. The professor made him read the books he worked on. As Mowery's technical education progressed so did his intellectual training. Each became a window on the other.

The basement room in the Folger Library holds suggestions of the Old World where Frank Mowery went to study. Then too there are assertions of this newer country-to which he returned to earn a living. The lighting is fluorescent, the tabletops Formica. On those tabletops sit stolid iron book presses. They look like instruments of persuasion remaindered from the Inquisition. Against one wall stands a cabinet filled with chemicals, its doors painted bright yellow in adherence to OSHA regulations. Against another, goatskins, waiting to be reincarnated as book covers, overflow a rack of shelves.

Between these antipodes sits the bookbinder, reviving the 400-year-old book. It is one of about 250,000 owned by the library, a collection that increases by about 2,500 volumes a year. It is also a collection which is not getting any less musty. The library owns at least one copy of two-thirds of all the books printed in English or in England before 1641. They intend to own the remainder some day. "Right now, I've enough work for the next 200 years," says Mowery.

So he taken it one stitch at a time, flattening the thread into the paper with the bone folder, adding pages to the growing text. While he works he talks. The conversation leads from the quality of paper during the Industrial Revolution, to book-binding in Dark Ages monasteries, and back to modern methods of paper restoration. What becomes apparent, between the deft progress of his hands and the sweep of the conversation, is the extent of Mowery's education.

What also becomes apprent is the extent and quality of his love for books. "I'd like to see people thing of books as physical works of art. But you can't put a book up on your friends, as you can a painting. Owning a rare and beautifully bound book is much more personal than that." He pauses and smiles sheepishly, perhaps fearful that there is too much edge to the idea, that he has been too assertive an advocate.

But then conviction again overtakes him. "Last fall I took $500 of my own money and started a separate conservation fund here. Materials are expensive these days. I didn't think the materials we were giving the books were as good as they deserved.

"I like history and the fact that people write things down. I like the idea that because I work on something it will be here 400 years from now." Pause-the diffiden smile. He speaks more slowly. "I'm lucky to be able to pass something on so far into the future. Most people can't do that through their work."

On the Formica tabletop nearby lie some books which have seen a few centuries and are now assured of transcending a few more. Among them there is what looks to be a paperback that has ridden around in someone's hip pocket too long. It is a first edition of Shakespeare's Venus and Adonis -the only known copy is the world. A piece of paper sticking out of it reads "unique."

Mowery picks the book up and cradles it in his hands like a small bird. "The pages of an old book like this are brittle," he says. "You want to let it open itself." CAPTION: Picture, No caption, By Bill Snead