It happens to many movies and this movie is no different. The book is better then the movie. In fact it is one of my favorite books. Russian Sci-Fi movies never had Hollywood class budgets so it is not surprising to see it less flashy then Star Wars. So the movie might lack visual effects but when you read the book you don't care about visual effects.
Now the spoilers(kind of): The movie (and the book) is NOT a space adventure. It is NOT a Sci-Fi detective story. It is about life of the people and how one event can change life of so many people. It is about what makes us human, how we look at unknown and what society is ready to do to individual people to keep everyone "safe". The action is set in the future but there is hardly anything would be different if it was at present days.
Another reviewer wrote that movie is not telling the reason for events. It is true but it is because the movie is only about the first book in the series. In the second book "Soft Mirrors" everything is explained but that is probably another 90 minutes (not 2 hours).
Review by bgertsberg from the Internet Movie Database.