I've never read the book to the film, so I'm going to review the film without such judgements.
The film's plot is about a depressed boy going through pressures in life, such as getting into a good school, dating issues, stressful parents. He thinks about suicide, but instead feels as though he should get checked into a hospital for some medication for his illness. Doesn't sound very funny, right? However, he finds that he must stay in a psychiatric ward for a whole week, meeting some of the patients who are more messed up than he believed he was.
Frankly, I had low expectations given the critic's reviews. But I think they got it wrong this time. This film is at times moving, with the main character, Craig, learning some life lessons along the way. Galifianakis, who plays Bobby (an adult patient who shares more in common with Craig than both of them realise) does an exceptionally great performance, expressing charm and amiability within every role. Newcomer Keir Gilchrist's acting reminds me a bit of Michael Cera's 2-dimensional personalities, but he has his own quirkiness that brings something new to the table. Emma Roberts, the female love interest of Craig is also likable, but I think she is a bit too cheerful to be playing a self-injurer.
The ending, while it leaves you wanting more, is feel-good and uplifting. There are moments of sadness mixed in with hilarity and ridiculousness, and somehow it never feels as though the two parts don't fit in together.
By far a different, but wholly satisfying film!