The first Saturday of every May means free comics.

Free comic books, ranging from the much-anticipated first issue of another Marvel’s “Avengers” Multiverse series, to the newest SpongeBob SquarePants installment to the latest “Fight Club” issue, are shipped internationally to specialty shops, just like those in Columbia, in an effort to gain new readers. Each participating comic book store is sent a box of the 50 free comic book titles from the organizers of Free Comic Book Day, the official day for beginners to start reading, regardless of age.

Rock Bottom Comics, the shop right above Fretboard Coffee on East Walnut, is preparing for war. Free Comic Book Day has always been a popular time for the small business.

“Two years ago, it was so busy — it was our best business day in 39 years,” owner James Cagle says. “I mean, it is a lot of fun, but it is work.”

The store only has two rooms, enough for perhaps 20 people if they wanted to be shoulder-to-shoulder with a neighbor. This doesn’t deter customers, though. Warrior customers brave the queues, which are usually 40 minutes long, to get into Rock Bottom Comics.

Slackers, Columbia’s fanboy/fangirl one-stop shop, is planning to keep things low-key — a simple spread of this year’s sample from “the box” of free comics every store is shipped, plus some extras that weren’t sold before the next issue was printed. They’re also serving food and drinks. Slackers is deciding to keep to what it does best and stay relaxed for the nerd holiday.

But that doesn’t mean all the stores are taking it easy.

Distant Planet is a little mom-and-pop shop that just opened its doors this February, and will celebrate its grand opening this Saturday. All 50 titles from “the box” will be given away, while special performance group Duct Tape Transformers (duct tape and cardboard cosplay DJs who do, actually, transform in their suits) entertains. Jim Yelton from 30 Minutes of Geek will welcome the new addition to Columbia’s surprisingly strong geek culture, and KCMQ radio is scheduled to report on the event. There will also be a raffle of Joker and Harley Quinn statues, with the benefits going to support the Buddy Pack program, a local food program that sends dinner home with food-insecure kids from school.

Because Free Comic Book Day falls on the day after “Avengers: Age of Ultron” opens in theaters, owners are betting on being busier than ever, especially due to the growing diversity in what is slowly becoming a mainstream art form.

“It’s not just top-heavy super heroines and barrel-chested …. I mean, it’s not just Tights and Flights anymore,” Cagle says.

More diversity and new voices are making comics more accessible to more readers, which he says is an especially important point for those who will get their very first comic book this weekend, complete with glossy pages, bright art and riveting adventure.

“It’s an exciting day for everyone,” Slackers manager Eva Quattrocchi says. “Especially those who aren’t already into comics.”