This is very clever piece of filmaking. I was impressed and it really kept me guessing. Based on the London based novel of the same name by Marie Belloc Lowndes, this is transposed to present day Los Angeles. Hitchcock made a film of the same novel in 1927, 13 years after its original publication. The 21st century version has some resonant echose of his work, but this is a different film altogether. Apart from working very well as an extremley dark thriller, it has some interesting and powerful things to say about madness and isolation(The strongest echo of Hitchcock from a much later film of his than the 1927 'Lodger' )It's a very well made film in every department. One you should see if you like excellent suspense films and don't mind them a little dark. Hope Davis one of the best actors working in the cinema at the moment gives an extraordinary performance in this film(which I think is oscar worthy) and the acting is uniformly very good. Daniel Ondaatje is a formidable filmaking talent.
Thinking of Hope Davis, I would recommend two of her other films if your like this. 'The Nines' and 'Arlington Road' are my next two suggestions, both of which are great and startling films.