Theron, who ironically has no Hollywood hookup (being drop-dead gorgeous was her golden ticket), plays Mavis Gary, an ex-prom queen from Mercury, Minnesota - a tiny burg meagerly existing outside the shadow of Mavis' new digs in Minneapolis. Mavis was the popular girl in high school but carries a bite that's typically the calling card of the alternative crowd (the character clearly inspired by scriptwriter Diablo Cody herself). Upon learning her former high school flame Buddy Slade (a rather generic Patrick Wilson) now has a baby, Mavis leaves the big city to slum in Mercury in an attempt to win back her old boyfriend - baby be damned. Along the way she meets her ex-locker neighbor from high school, Matt (the much overhyped Patton Oswalt), a schlub that Mavis uses to bounce her zany "rekindling with Buddy" ideas off of. Round and round they go, with Mavis devolving more and more by the moment - culminating in a surprisingly powerful revelation that gives Mavis a somewhat tragic bent. Theron crushes the role, channeling her best 'Mean Girls' impression, providing Mavis a riotously self-centered persona. But Reitman and Cody let Mavis' character off the hook - she doesn't do a 180 - it's a full 360.
Cody's script often feels akin to a rough draft - aside from Mavis, the characters are on the page but they aren't fully realized in a way that evokes a level of involvement that's maximally impactful. Theron is stellar and may very well get a nomination for her work but 'Young Adult' itself isn't worthy of one. It has the elements of being something special but in the end simply serves as a serviceable vehicle to showcase Theron's ability to once again show that she's infinitely more than just a pretty face.