Paul Derrick’s review published on Letterboxd:
Room is a simple story that will hit you hard. Brie Larson plays a young woman (Ma) who was abducted and has been held captive in 'Room' for 7 years, where she has subsequently given birth to her son Jack. Jack has never been out of Room and knows nothing else.
We see how they cope in day to day life in Room, as the captor brings them basic rations every day. Throughout the film it is left to our imagination as to where exactly they are and what is the reason why. Jack believes that the outside world is non existent and anything he sees on TV is not real. Jack is key to their escape so his mother has to explain the situation very carefully to him in order for him to grasp that the outside world is indeed real.
The pacing of the film is very good, we pretty much have two halves: the first half starts straight away with the pair in Room, we see them go through many different emotions in their fight for survival. Then they plan the escape (which if you have seen any trailer for the film you will know that they eventually escape anyway so it's not a spoiler). The second half of the film is about both of them adjusting to the outside world. Ma going back to family life and facing struggles as her father can't even look at Jack. Thankfully her mum and mum's boyfriend are much more supportive and really help Jack along the way.
The acting is terrific throughout the film which gave it a lot of realism. I do wish that the film had perhaps been a bit more detailed, we could've had another 20-30 minutes which could've explained briefly how the captor took Larson, what exactly happened to him at the end and how he was caught, a few bits of news/interviews detailing the fact that she was missing, search parties for her, was anyone ever suspicious of him etc. And also a bit more of Ma and Jack as he was younger just to get a sense of even more struggle they went through and then perhaps a little segment at the end of him growing up in the world. Overall an amazing job by Jacob Tremblay one of the best child acting performances I have ever seen. Yes the movie lacked in some parts but I believe that Tremblay and Larson really made this movie worthwhile.