Marvel Super-Heroes Secret Wars was a promotional concept used to combine Mattel's desire for a Marvel toy tie-in and the readers demands to see all the heroes and all the villains in one big battle. Jim Shooter wrote the 12-issue series and orchestrated it throughout the Marvel Universe.

Officially, the Secret War itself did not cross over into any of the other Marvel publications. A handful of books referenced strong surges of energy as a precursor to the pending fight on Battleworld.

The characters in their own books disappeared at the end of one issue and reappeared in the next issue already back from the Secret Wars. Some of them carried the repercussions of the Wars. Spider-Man had a new black costume that would soon become Venom. Hulk had a broken leg and was on a crutch. She-Hulk was now a member of the Fantastic Four because The Thing was still on Battleworld. Iron Man has some new armor and another Spider Girl appears.

None of the regular Marvel titles had anything on their covers to indicate they were related to the Secret Wars and the SWI books themselves did not require you to pick up another title to continue the story.

There are some things to keep in mind when viewing the SWI checklist. Some items on the checklist like Spider-Man 249 and Avengers 241 are considered optional because they only touch on SWI in one or two panels. The Thing 11-22 is not considered optional for two reasons. First, all of those issues take place on Battleworld. The second reason is that those issues dive deeper into the explanation of why things happened the way they did during the Secret Wars.