As far as my knowledge this is the second attempt for Marvel to create a "template" for today's event storytelling.
After the Contest of Champions, Jim Shooter wanted to make a story that will cary its legacy to next step with a more compelling adventure.
In the Contest of Champions, there were simply a brawl between heroes, but in the Secret Wars, the event is a bit more universal.
Heroes are taken to a distant planet called "Battleworld" and it's ultimate fight between good and evil. However the story goes deeper as it progresses. You witness X-men's unwillingness to fight and their reasons behind it, rise of Molecule Man, and all other stuff.
Simply, Secret Wars is a basis they used to make a storyline where it's joined by the current character roster and it was the first step to create a larger, company wide event with a limited series leading the story, and other titles become tie-ins.
In short, it's a must-read for any Marvel fan, not only because it's a good story, but also it's a project where you can see how Marvel took its first steps to create today's giant 6-month-running events.
Reading Order
1- Secret Wars 01
2- Secret Wars 02
3- Secret Wars 03
4- Secret Wars 04
5- Secret Wars 05
6- Secret Wars 06
7- Secret Wars 07
8- Secret Wars 08
9- Secret Wars 09
10- Secret Wars 10
11- Secret Wars 11
12- Secret Wars 12