It takes place a little after the comic's ended. Unfortunately, or fortunately depending who you ask, the movie didn't end the same way so if you haven't read the first series it may/will be a little confusing. That being said, it takes the next logical step in a story where the premise is real life people wanting to make the world a better place by becoming real super heroes. That next logical step? Super hero teams.
It starts by showing an event that is going to happen in a later issue, but just little enough to leave you curious for more. Still easy to identify with the main character if you're a comic book nerd. Hit Girl's story is intriguing. I, for one, am really interested to see how it plays out after the first series. Especially after the unfortunately omitted elevator scene with her; I just want to know how that affects her.
I'd highly advise to first read the first series, then continue with this one. Of course my opinion could change as the series continues, but so far the first issue of this six parter is a good start.
Edited, Oct 24th 2010 2:13pm by lolgaxe