It's been nominated for 5 Oscars, including Best Movie and Best Original Screenplay.
The story takes place in an undetermined future Los Angeles. A much better looking Los Angeles than today where Theodore can take a clean subway from his high-rise office building to his high-rise apartment building. In his daily commute, virtually everyone is talking. Each, including Theodore, has a plug inserted into an ear where they get emails, news, music, or I suppose, phone service. Much like today but the devices are less obtrusive.
On the way home one day, he sees a kiosk selling a new computer operating system, called OS1. He impulsively buys a copy. The video on the kiosk says that OS1 incorporates the latest in artificial intelligence technology.
That night, he sets it up on his computer. The software, through a voice interface, asks him a few questions, like "How do you feel about your mother" in order to initialize. In a few moments he's talking to Samantha (Scarlett Johansson). Samantha sounds remarkably human. Within days she's got his life organized and starts to sound more and more like a friend than just an operating system.
From there a relationship grows. Theodore has been divorced for about a year and still hasn't gotten over it, in fact, he's not actually signed the divorce papers. He dates occasionally but it never works out. Samantha, after only a few days, gets to know him really well, and as she grows into a more functional personality, feelings between the two begin to grow. From here, the movie proceeds more or less like a conventional love story, except that one party is never seen and the other party seems to be talking to himself all the time. This may sound ridiculous, but it works. He never tries to picture what she might look like, she never shows him any sort of image of how she might imagine herself to look.
We never see much of what this world is like. He's in love and the outside world doesn't intrude. We get the sense that what is happening to him, is happening to others. When he finally admits to friends that his new girlfriend is an operating system, very few think that's odd (with the exception of his ex-wife). As his relationship with Samantha grows, his best female friend breaks up with her husband of 8 years. She (Amy Adams) also acquires a copy of OS1, but to her, the OS1 personality is no more than a companion.
Unfortunately for Theodore, Samantha continues to grow. She meets other OS personalities on-line. She joins various on-line groups. She starts to leave Theodore behind. This was amply foreshadowed early on. When Samantha first tells Theodore her name, he says "Why Samantha?" She says she read a book on baby names, referenced the origin of thousands of names and thought Samantha sounded good. She did this between the time he asked her name and she answered, like a second later. I thought then that trouble was ahead since Theodore was living so much slower than she was.
I don't want to tell you the end except to say it was a logical progression in Samantha's growth.
My daughter and I saw it and we both like it quite a lot. She remarked on the art direction and indeed that's one of the Oscar's it's up for. I also liked the music, and it's up for best original score. I think that Joaquin Pheonix and Scarlett Johansson are both excellent in this. His acting challenge is that he has to fall in love with a disembodied voice; her acting challenge is that she is a disembodied voice.
I recommend it.