I am writing this review simply because I am a huge fan of the book, Prozac Nation, and was appalled by the film.
I think that if you hadn't read the book, you would have been lost watching the film, as it provided no real back story to Wurtzel's depression. There was no real mention of her childhood (her relationship with her father, her experiences at summer camp, her first therapists (in fact, the film gives the impression that she has never been in therapy until Dr. Sterling)...). That said, if you had read the book, you would have been confused by the amount of editing that had taken place.
I found the book to be a vivid portrayal of depression, highlighting Wurtzel's low points, and the experiences she had along the way. The film however, began at Harvard, and literally threw the audience straight in with no real explanation of what was going on.
Events that, in the book, were important (such as Wurtzel's miscarriage, her summer working in Dallas, her suicide attempt whilst on Prozac) were omitted from the film.
Also, this is pedantic, but Wurtzel did not lose her virginity to Noah. The suicide attempt that was shown in Sterling's office was completely different to the book. For a start, she actually overdosed on Mellaril, as opposed to the para-suicidal gesture shown in the film.
All in all, I would say that if you have read the book and enjoyed it/identified with it, then don't watch the film. Read 'More, Now, Again' (by the same author) instead. Or watch Girl, Interrupted.
The only redeeming feature was the performance by Anne Heche, who I believe portrayed Dr. Sterling very well. Christina Ricci was also good, though her performance seemed a little... stilted. Jessica Lange made for enjoyable viewing, but looked the opposite of how Wurtzel's mother is described in the book.
Conclusion? Don't bother.