For Marvel, when it comes to special events, they tend to approach it three deep, in that you have:
The main thrust of the event itself: for Civil War, there is just the comics dedicated to the event itself. Those are easy enough to find, considering there's a glut of trades scattering around now. So you can just buy/ read the trade that has the civil war itself.
A spin off from the events itself: For the event of Civil War, there's Frontlines part one and two - you don't need to read those. It's basically about Ben Urich and his team covering the war and being 'on the ground' so to speak.
Tie in issues of specific titles related to the event: So you have Civil War: New Avengers, Civil War: Iron Man, Civil War: Spiderman, et al.
Well, it goes a little something like this...
The main thrust of the event itself: for Civil War, there is just the comics dedicated to the event itself. Those are easy enough to find, considering there's a glut of trades scattering around now. So you can just buy/ read the trade that has the civil war itself.
A spin off from the events itself: For the event of Civil War, there's Frontlines part one and two - you don't need to read those. It's basically about Ben Urich and his team covering the war and being 'on the ground' so to speak.
Tie in issues of specific titles related to the event: So you have Civil War: New Avengers, Civil War: Iron Man, Civil War: Spiderman, et al.
That's as simple as I can explain it to you.