It's a great title, interfering slightly with the rules of grammar. It takes place during the 60's, when, of course, rules more significant than those of grammar are being challenged. She also challenges common sense, mixing too much aspirin and alcohol. Her parents, understandably highly perturbed, sent her to a place where she would be looked after very, very closely. It's based on a true story, the memoirs of Kaysen's stay in a mental hospital in the 1960's.
Memoirs are a strange hybrid of fact and narrative.
The unifying theme isn't a plot per se, but the fact that the accumulation of insights and anecdotes are true. The form works well for a book, which can provide all the necessary details, but as a movie, without the suspense of a plot, the whole is less than the sum of its parts. Which is unfortunate, because some of the parts are quite good. Winona Ryder is Kaysen. Her role in front of the camera is a good one, but not a great one.