Among the publishers taking part in the giveaway are Marvel, DC and Dark Horse.
The event, which began 11 years ago with four publishers, is designed to draw new readers into comic book stores. Now, 40 publishers take part in 46 countries.
More than one million people flocked to shops last year, which was double the number from five years ago.
"This grand plot for world comics domination is continuing to steam roll," said Joe Field, who owns Flying Colors Comics in Concord, Calif., and helped launch the annual event.
"We're adding people, we're adding countries and we're adding comics," he said Friday. This year's titles range from Boom! Studio's "Peanuts/Adventure Time Flip Book" to Rebellion's "2000AD Judge Dredd Special" to Dark Horse's "Star Wars/Serenity" book.
The annual event is also an attempt to foster community among longtime readers.
The Associated Press contributed to this report.