On Sunday, Marvel Comics announced that it was making 700 of its #1 comic books — including titles based on heroes like Spider-Man, Iron Man, and the Incredible Hulk — available for free until Tuesday at 11 p.m. EST.

Of course, it's something of a promotional stunt, designed to draw attention to Marvel's digital comics collection, which can be read on tablets and smartphones. (Comics can be downloaded at Marvel's website, or through Marvel's free mobile app.) But the giveaway is also a big boon for fans.

Now, we know the world of comic books is so expansive that it can prove overwhelming to the uninitiated. With 700 comics available, where should you begin? Here's your cheat sheet:

1. Marvel NOW!
Any fans looking to catch up on the latest stories set in the Marvel universe should grab the first issues of the company's Marvel NOW! line, which launched in 2012. Highlights include Uncanny Avengers, which features superheroes including Captain America, Thor, and Wolverine, and The Superior Spider-Man, which follows the hero while his body is under control by the villainous Doctor Octopus.

2. Classic comics
If Marvel's latest plot developments don't do anything for you, you can always take a trip back in time and see how your favorite heroes began. Try 1962's Amazing Fantasy #15, which features the first appearance by Spider-Man (and is thus being counted as a #1 for the purposes of this promotion); 1963's Avengers Vol. 1 #1, which spawned the superhero lineup that earned more than $1 billion at the box-office last year; and X-Men #1, which introduced the legendary mutants in their first adventure as they squared off against Magneto.

3. Weird comics
Try something like A-Babies vs. X-Babies, which follows clashing, toddler-sized versions of the Avengers and the X-Men. Or Spider-Man: Back in Quack, which teams Peter Parker up with Howard the Duck? When the cost is $0, there's no better time to indulge in the weirder side of the Marvel universe.

4. Non-superhero comics
Though the free download list is tilted toward Marvel's superheroes, there are a few intriguing options for those who prefer their comic heroes to be cape-less. Jane Austen fans can download comics based on Pride and Prejudice and Emma, and there are several available series set in L. Frank Baum's Oz.

5. Choose a comic at random
These 700 comics will only be free for another day (at which point they'll be added back to the store, with each issue ranging in price from $1.99 to $3.99). But as long as they're free, why not replicate the feeling of wandering into a comic book store and pulling something you'd never normally read off the shelf? Pick a title at random and give it a shot. You might surprise yourself.