Although the story has enough intrigue to keep your attention, it is heavily driven by dialogue and would probably work just as well as a theatre production or radio play. And because McGregor's investigation relies so heavily on written evidence, we end up having to read along with him - including watching him search the web for a few minutes as he tries to work out the connection between the PM and a supposed CIA agent. Also, for a so-called thriller, there is really little in the way of tension or indeed thrills. Apparently the movie cost $45m to produce. Most of this must have gone on actors' fees, for there is no evidence of extravagance in the set and special effects are almost non-existent.
The acting is largely decent but both Cattrall and McGregor struggle at times with their respective English accents, Cattrall resorting to speaking constantly like a Sloane in the dentist's chair - "you do raahlise haaw saahrious this is getting, don't you?", she asks him at one point - and McGregor adopting a bizarrely fey mockney twang. This is particularly noticeable in scenes involving just the two of them and left me wondering why McGregor, at least, wasn't allowed to talk with his own voice.
In short, The Ghost is a film that keeps your attention and is, on the whole, worth watching - but I'm sure it will be just as worth watching when it arrives on TV in a couple of years, and there is no pressing reason to seek it out sooner than that.