imdb) Each of the 3 parallely told plots is complicated and erratic (as usual no spoilers, you can find s synopsis here wikipedia). To make it more complicated, the three different story lines are set in Italy (Rome and Taranto, a place in Southern Italy), Paris and New York.
Paul Haggis, director and writer of the movie, declared in a Q&A session at New York´s Sunshine Cinema Theater that he had worked 2 1/2 years on the script. He "must have written fifty drafts", reports Wikipedia. That explains that the final product looks somewhat overcooked.
But anyway, the movie isn´t boring and sometimes funny and romantically. I enjoyed the cinematography. Gianfilippo Corticelli, the cinematographer, captured the different locations - with diverting lights and colors - beautifully. It was joyful to watch the frequent switches between Italy, Paris and New York - even that the film almost completely was shot in Rome and it´s legendary Cinecitta Studios.
The cast also was a plus, even that I think that Liam Neeson, as one of the lead characters, is a bit overused in today´s cinema. Adrian Brody, as an American somewhat lost in a kind of exocital Italy, was fun to watch, Olivia Wilde was a real eye cooky and I would like to see more of the newcomer Loan Chabanol.
"Third Person" is an entertaining movie but also an example that to much ambition can endanger the career of a director.