50/50 is a comedy drama about cancer and just like the disease, the film was always going to be a tough "cell". Thankfully however, it succeeds due to a delicate balancing act between comedy and tragedy plus a superb lead performance from Joseph Gordon Levitt.
Reiser's script and calm direction from Jonathan Levine do a terrific job in not letting the comedic moments overshadow the seriousness of the story, so that when Adam's condition worsens, we are emotionally invested in whether he survives or not.
Much of this connection with Adam is the result of a terrific central performance by Joseph Gordon Levitt. Fast becoming one of the best actors of his generation, Levitt makes Adam very down-to-earth and relatable which makes him easy to identify and empathise with. Plus he is the first cinematic character I know of to bite his fingernails which is a habit that I have (and my friend Linny is constantly trying to break me of!). It is a very understated performance, not prone to Oscar-worthy showboating scenes that other actors may have been tempted to do, instead opting to slowly draw you into his plight so that when he breaks down in front of his mother just as he is about to go into surgery, his tears are not the only ones flowing in the cinema.
There is fine support from Seth Rogen as Adam's best friend. Some may complain he is recycling his "schlubbenly, profanity-laden goof" schtick but since he actually helped Reiser through his own cancer struggle, he is essentially playing himself and in my opinion it is the best he's ever been, bringing a warmth and sincerity to the film.
If you were to find fault with the film, the female characters suffer in that the screenplay tends to have them conform slightly to Hollywood stereotypes (bitchy girlfriend, neurotic mother, etc) and the potential romance with the therapist feels a little forced but wisely left largely unconsumated. Also it is a shame that a potentially interesting family dynamic due to the father's alzheimers but nearly every film this year has already used it (by that I mean Friends With Benefits and Love And Other Drugs).
However these are minor quibbles with a moving film with a lot of heart that can deliver an emotional suckerpunch through all the laughs. And that should be congratulated as the odds of finding a film that can successfully make you feel the full range of the emotional spectrum are certainly not as good as 50/50.