A few months ago, Minneapolis writer Kate DiCamillo shared a photo on her Facebook page. It was of a library card — not the kind used to check out books, but the kind that used to be kept inside a manila pocket in the front of every library book.

The title of the book was typed at the top, and if you wanted to bring the book home you wrote your name on the card and handed it to a librarian. The librarian filed it in a long wooden box and then stamped a date on another card, which she slid into the manila pocket. That was your reminder of when to bring the book back.

This is how Kate DiCamillo, and all of us, used to do it back in the day.

So imagine the time traveling inspired when a librarian from DiCamillo's old grade school came to one of her readings with a library card in hand. It was for "Mary Poppins Opens the Door," by P.L. Travers, and there, printed neatly in pencil on the second line, was the name Kate DiCamillo. She had borrowed that book back in the 1970s, and now here was the card, given back to her, a little bit of her own history.

"Thank you, Clermont Elementary Library," DiCamillo wrote on Facebook. "You opened doors for me."

It is impossible to look at that card without a deep pang of loss. While Kate DiCamillo was haunting libraries down in Florida, I was up in Duluth, haunting libraries of my own: Endion Elementary School, Woodland Junior High, the Duluth Public Library.

It wasn't just the books that I loved (though I loved those deeply), but everything: the fussy accoutrements — the little stamps with the inky rollers that changed the date, digit by digit. The wooden magazine rack, where you could look at all those magazines you didn't get at home. The tiny-type Readers' Guide to Periodical Literature, where, once you cracked the code, you could find any article you wanted, by author, topic, or title.

Everything about a library opened doors, let in light, told you more than you had ever expected to know.

Perhaps best was the card catalog, with its smoothly gliding dovetail-cornered wooden drawers. You could spend a lot of time flipping through those cards, looking up one thing and happening upon something else along the way. One wrong move, stopping one card before your goal, could send you in an entirely different direction, toward books you'd never dreamed of reading, topics you knew nothing about.

Sometimes there were spidery handwritten notes on the catalog cards, and sometimes cards had been flipped over and re-used, so on the back were notations for other books long since pulled from the stacks.

Those card catalog drawers were filled with history and possibility.

Nicholson Baker loved them so much he wrote about them for the New Yorker. (Jettisoning card catalogs, he wrote in 1994, is a "national paroxysm of shortsightedness and anti-intellectualism.")

I don't mean to be all Luddite and sentimental here. Computers are fast and efficient; digitizing photos and newspapers and obscure books has helped make research so much easier (and Baker would agree); librarians still do important work, just with different tools. They still want to lend you books, share knowledge, spread information, open the doors and let in the light. (They have the worthiest job in the world, I think.)

But I do miss the rubber ink pads and the manila pockets. And I miss the old card catalog, the neatness of its typed cards and the orderliness of its alphabetization belying all the wild possibilities inside, allowing for stupendous accidents, and joyous serendipity and life-affirming, life-changing mistakes.

If you don't have a library card, you should get one. If your kids don't have one, you should urge them to get one. Go together. Pick out books. Let in light.

Laurie Hertzel is the Star Tribune's senior editor for books. On Twitter: @StribBooks. On Facebook: www.facebook.com/startribunebooks