"California Bookstore Day's logo is a super-cute little bear," said Independent Bookstore Day cofounder Pete Mulvihill. "My favorite thing that happened on the first Bookstore Day was someone hand-sewed a bear, decorated it, and took it to every bookstore that was participating in the event. We had reached the real, true, hardcore book nerds. It's just a giant, fun party."

Mulvihill and his wife, Samantha Schoech, spearheaded the organization of the first California Bookstore Day in 2014, inspired by the phenomenal success of the annual Record Store Day project.

Mulvihill is one of the co-owners of Green Apple Books & Music's two stores in San Francisco. Having witnessed what Record Store Day does for sales in Green Apple's music department, and its ability to draw crowds in an increasingly digital media marketplace, Mulvihill thought, why not throw a similar celebration for books? Schoech, a writer and editor, volunteered to produce the event.

"I thought, 'Literature deserves the kind of party record stores get,'" said Mulvihill, "adapted to bookstore culture."

San Francisco's California Bookstore Day, funded by the Northern California Independent Booksellers Association, was a tremendous hit. There were lines down the street, with sales rivaling the week before Christmas. As with Record Store Day, bookstores and presses designed unique items for sale only during the event. "We had some towels made with literary quotes on them," said Mulvihill. "For advertisement, we made a Don DeLillo graffiti stencil that said, 'California deserves whatever it gets.'" Mulvihill's favorite: a literary map of the world's oceans, illustrating the settings of famous seafaring novels like Moby-Dick.

This year, Independent Bookstore Day is going national. More than 400 stores are participating—Mulvihill isn't sure how many states will be involved, but was amused to learn Kentucky chose its own date for the event, as the national date (May 2) conflicts with Derby Week.

An array of Seattle-area independent bookstores are eagerly preparing to participate. The beloved Elliott Bay will provide a relationship-advice booth with "mystery guests," Island Books will host a scavenger hunt and collective short-story writing on vintage typewriters, and several stores, including Fantagraphics and Open Books, will offer free books or two-for-one deals. Many stores will host trivia and literary Mad Libs and serve food and drinks (in the IBD press release, "cake" was the only word followed by an exclamation point).

The main event, however, is the "Indie Bookstore Challenge," wherein anyone who visits and has their "passport" stamped at every store gets a chance to win a 25 percent discount at all of them for one year. "I love what Seattle is doing," said Mulvihill. "Stores that would normally be competing with each other are cooperating. I can't think of anything else like it. I don't think, for example, coffee shops get together and share their best techniques." (He noted the irony of Amazon being headquartered in a city with so many independent bookstores.)

One of the benefits of the project is the sense of solidarity among the participants. "We feel a bond with other indies," said Open Books co-owner John Marshall. "Heck, Amazon has even made Barnes & Noble seem like a relative—what dark magic does that? We are pleased to celebrate shared DNA with our sibling stores."

In recent years, Record Store Day has been criticized for the increasing involvement of big corporations. While plenty of good music has been put out as Record Store Day–exclusive releases, many believers have lamented the event's turn away from celebrating the mysterious thing that makes records and record stores bewitching.

The owners of participating bookstores seem wary of these pitfalls. "I hope Independent Bookstore Day can avoid the unfortunate 'treasure hunt' mentality that has tainted Record Store Day—an effort that began as an appreciation of stores whose very existence became tenuous because of new technology," said Fantagraphics manager Larry Reid. "It quickly became dominated by large corporate interests that have no interest in the economic well-being of record stores (or musicians, for that matter). Independent bookstores face many of the same challenges as record stores with the rise of electronic platforms and online retailers, which suck the soul out of the literary experience."

Mulvihill isn't as worried. "I don't know what the future will bring," he said. "But I don't think [IBD] will become some empty vessel for what publishing companies want to do."