Hugh Grant, as usual, has its way with words, but his volume is pretty moderate this time around. Opposite him is Nicholas Hoult as the boy. Their character are very disparate if not entirely opposite, and they play this duality pretty well, one strengthening and helping the other finding some basic truths of life.
All the acting is solid, to the point where you want to slap some sense into Toni Collette's depressive persona. The editing gives us a great pacing, and the story is engrossing and, even if it stays pretty simple, brings a couple of new things to the table, as well as some well worn out ideas. The "lie" makes an apparition, but is dealt with in an incredibly mature way. The environment is rich, the important characters deep, the soundtrack sensible, and you'll chuckle a good number of times.
I highly recommend, except if you're looking for action or if you want to avoid sentimentality.