There are a lot of ways romantic comedies can go wrong, and Crazy, Stupid, Love avoids nearly all of them. For a PG-13 movie, it's kind of raunchy (MPAA: "coarse humor, sexual content and language") but it's also very funny. A lot of the humor is situational, but a gratifying amount springs from its six primary characters, none of whom fall into the caricature trap. (There are also strong performances from supporting characters.)
Here's the story: on a "date night", Emily (Julianne Moore) announces to her husband Cal (Steve Carell) that she (a) wants a divorce and (b) has been canoodling with co-worker David (Kevin Bacon). This immediately impacts their kids, most notably 13-year-old Robbie (Jonah Bobo). Robbie has a major crush on his sitter, 17-year-old Jessica (Analeigh Tipton); who, in turn, is smitten with Cal.
Bereft, Cal starts spending time in a bar, drinking too much, and regaling the other patrons with his misery. This proves too much for fellow patron Jacob (Ryan Gosling), who is perhaps the smoothest one-night stand artist you'll see. We only see him strike out with one woman, Hannah (Emma Stone). Jacob takes Cal under his wing; soon enough, he's filling his nights with female companionship. But he still pines for Emily. (Cal's first "success" is with Kate, who's played by Marisa Tomei; her brief scenes are probably the best part of this very good movie.)
The movie (I think successfully) walks a fine line: while showing the misery of infidelity and marital breakup, it doesn't forget to be funny. Without spoiling things, it also has a couple of Dickensian coincidences that are successfully played for laughs. Just keep your eyes open.