Growing up is not so glamorous in “Young Adult”

She receives an email from her high school sweetheart, Buddy Slade (Patrick Wilson), who has just recently had a baby girl with his wife. Gary decides to return to her hometown to save Slade and reclaim her lost love. After all, this is her version of “happily ever after,” and the reality in her mind is that true love can conquer anything — even marriage.

It is suffice to say that with “Young Adult,” Diablo Cody has matured into a very talented writer. Her first screenplay, “Juno,” also directed by Reitman, may have won her an Academy Award, but it was bogged down by dialogue that one might read on UrbanDictionary.com instead of the vocabulary of a regular teen.

Something about “Young Adult” shines brilliantly, however. Even when Cody uses words like “KenTacoHut” — to describe a KFC, Taco Bell, and Pizza Hut all under one roof — it does not feel entirely out of place.

Gary might be in her 30s, but her mind seems to have stopped developing mid-high school. A woman whose qualities include binge drinking and coming into her old hometown to destroy a marriage and family is not one that you would want to sympathize with, and neither Cody nor Reitman ever take a step at making her a likable character.

What makes Gary so wretchedly entrancing, however unsympathetic a character she might be, is Theron’s award-worthy performance. The role requires her to be an attractive woman, which she definitely flaunts from start to finish, but one with an entirely spiteful personality.

You never really want to care for her, and by the end, you have pretty much sided against her completely, but there is still enough humanity in her to keep you wondering whether or not your life might come crashing down to this point some day.

Theron is not the only stunning actor in the film, as Patton Oswalt, who is best known for his role in “The King of Queens” and his stand-up, shows off just how great he can be in a dramatic role.

In their high school days, he was the complete opposite of the blossoming and popular Gary: a short, overweight nerd who was beaten during high school. Now, his character Matt is in some ways just as emotionally stunted as Gary, another alcoholic who cannot escape the past.

As for Wilson and Elizabeth Reaser, both play their parts well. They give us people that we can actually grow to like and provide such a striking contrast to Gary that we cannot help but want her to fail in her devious goals.

Reitman, whose last film “Up in the Air” scored him an Oscar nomination for directing, reminds us just how well his partnerships with Cody work by showing us this raw and realistic tale. It would come as no surprise to anyone if the film brought along a few more Academy Award nominations, or even a win, for Reitman, as well as Cody for writing, and both Theron and Oswalt for acting.

While it may seem like just another dark comedy, “Young Adult” is a harsh film that just happens to be well-dressed enough to not reveal how miserable its characters really are.