Runaways has a really strong opening. The first six issues are fantastic, and do a great job of setting up the cast, the premise, and the stakes, with wit and heart. It's been a long time since I've enjoyed a cast of characters so much, in comics or prose, and the titular Runaways were likable, sharp protagonists. I'm not big on kids in general, and obviously kid lit isn't really my thing, but despite ranging in age from eleven to sixteen, the protagonists of Runaways manage to avoid falling into typical "child character" traps of being whiny or annoying or excessively naive or stupid. And while the premise plays out like a childhood fantasy - who didn't daydream as a kid about running away to live in a sweet-ass clubhouse without rules or restrictions? - the details of the situation and the kids themselves keep the story from tumbling into cheesy Disney Channel/Spy Kids-esque territory. The characters - their flaws, indecision, and bonds - keep the story grounded.
The diversity of the team here is so fucking refreshing, too. As you can (mostly) see from the group shot on the cover, the Runaways are quite a varied group. Our team includes four girls - one Japanese, one overweight, one a lesbian - and is lead by an African-American boy genius. No stereotypes in sight (er, Gothic Lolita Asian girl aside, but Vaughan has fun with her and a few Magical Girl tropes), and their powers are just as varied as the characters. It's a fun mash-up, really. You've got aliens, time-travelers, sorcerers, mad scientists, mutants, and plain old evil geniuses. My personal favorite power had to be Gert's: her parents traveled to the future to buy her a genetically-engineered telepathic raptor that she names "Old Lace".
There is nothing about that that is not awesome.
Unfortunately, while the first volume of the series ends strong (at issue six), the story kind of unravels from there. Volume two - issues seven through twelve - feel a lot like filler, and the logic behind the plot becomes very...loose. Things happen because the plot says so, and the relationship between the two lead characters, Nico and Alex, lacks in real development, and progresses far too quickly. One second they have a crush on one another, the next they're declaring their love. I mean, I know they're teenagers and infatuation and all that, but we barely even saw them spend any time together!
And I hate to say it, but following issue six, the story felt a little more...childish? It seemed like it didn't have to go into too much detail about the "hows" and "whys", perhaps because kids don't really think so hard about that sort of thing. Cartoon-logic, I'd say; there are some weird plot holes involving foresight and prophecy. However, this may also have something to do with the rather odd progression of time in the book - weeks pass between issues, so when reading in a collected format, the events end up feeling more condensed than they actually are, in-world.
The book also frequently falls prey to exposition speak. It's a common problem in comics, where writers will feel the need to have characters recap the last issue's events in stilted dialogue, to refresh monthly readers or bring new ones up to speed. We get the "what we're doing now and why" speech pretty frequently throughout the series, and I swear to God, a couple times we got it more than once per issue.
I was also pretty disappointed that this particular story arc never really expanded on the initial idea of the kids fighting crime to make up for their parent's mistakes. Given the outcome of the story, even though the team goes on to do so in future installments, you still kinda lose that redemption and oppositional dynamic with the parents.
Still, the arc has a pretty satisfying, if somewhat predictable, ending, and I liked that the book didn't go out of its way to demonize the kids' parents. Yes, they were evil super-villains bent on destroying the world, but they were also parents who loved their children, and that was more important. It's actually kind of rare to see cackling, mustache-twirling, bona-fide supervillains humanized in such a way, and I liked that. It's a bittersweet sort of ending, but it's also a relatively empowering one for the characters.
I'd definitely recommend Runaways to anyone interested in perhaps dipping a toe into shared-universe comics. There's absolutely no Marvel history or continuity you need to be aware of the enjoy the series - though they do become more heavily involved with the Marvel universe in later volumes - and it's probably relevant to mention that Joss Wheadon takes over writing the series around that point. I haven't read his run yet, but I am looking forward to reading more Runaways in the future.