Marvel Unlimited, Marvel’s digital comics subscription service, is currently offering all fans free access to some of Marvel’s most iconic stories from recent years, including now-classic Marvel Comics events and critically acclaimed runs featuring the Avengers, Spider-Man, Black Widow, Captain America, Captain Marvel, and more.

With that in mind, I’ve decided to take a look back at these classic stories and maybe help you decide whether or not you would like to check them out. Our next series is one of the biggest crossover events in the history of Marvel Comics. Skrulls have infiltrated Earth and are disguised as some of our favorite heroes. How can the heroes fight, when they don’t know who they can trust?

Secret Invasion

The Avengers have made a horrifying discovery. While on a mission in Japan, they killed the legendary fighter known as Elektra. Only it wasn’t Elektra. The result was much worse. It was a Skrull impersonating Elektra, leading Tony Stark to believe many, many others could have been replaced by Skrulls as well.

When a ship crashes in the Savage Lands the New Avengers investigate and are very surprised by what they find. A group of Earth’s mightiest heroes step off, some of them greeted by copies of themselves. Now, two teams face off, with no one on either side knowing who they can trust. And that’s just the beginning.

The heroes are overwhelmed by the sheer numbers and surprise of the Skrulls. Luckily, they’re not alone. Turns out it’s not only heroes with a lot to lose if the Earth is taken. Villains have some stake in the fight as well. Norman Osborn’s Thunderbolts and the Hood’s gang of street villains join the battle as well. And of course, Nicky Fury and his Secret Warriors are always around when the fate of the world is at stake. Now they just need to figure out who they can trust.

There have been a lot of major crossover events in Marvel Comics, in which our favorite heroes have teamed up to take on menacing villains. The Skrull empire may not have the power of Thanos or the Beyonder, but they’re ability to destroy Earth from within makes for a much more intriguing story.

“Secret Invasion” is right up there with the biggest events, like “Infinity Gauntlet” and “Civil War.” In fact, Spider-Man sums it up nicely when he explains that if something really big is going on, Uatu the Watcher usually shows up. Of course, he says that to reassure himself that this isn’t a big deal only seconds before he actually shows up. Classic Parker luck.

There are so many components to this story, with dozens of fan-favorite characters playing huge roles in the story. Tony is the one Earth relies on to protect it, Spider-Woman can’t be trusted, Clint Barton’s past comes back to haunt him and Norman Osborn is trying to save the planet with an ulterior motive.

It’s a very complex story with a lot of layers to it. You can absolutely enjoy the story just by reading the eight issues, but there are also dozens of tie-ins that further the story and fill in a lot of gaps. “Secret Invasion” also launches more major storylines moving forward. If you’re a Marvel Unlimited subscriber, you’ll probably want to keep on reading when you finish the story.

You can read “Secret Invasion” for free now. And be sure to check out some of our other looks back at other classic Marvel Comics here.