Mad Detective isn't an easy film to get to grips with. Throughout the investigation we aren't sure whose perspective is correct: whether the mad detective himself is simply having visions and he is wrong, or whether his insights form a true representation of what is going on in the world. You don't find out until the final shoot-out scene, and then it becomes horribly obvious which is true.
Without the 'I see inside people' supernatural/insane aspect, this film is a very straightforward Hong Kong police procedural. But the fact that it centres around an ex-policeman so bonkers he cut off his own ear makes it convoluted and intriguing. Just like the Sixth Sense, much of the Mad Detective makes much more sense on second viewing. But unlike the Sixth Sense it is devoid of Hollywood's flourishes and over-statement, so instead the beauty of the film comes across from the nuances of the actors' performances. The scenes with the mad detective's wife are especially heart-rending -- their final goodbye in particular.
There are parts of the Mad Detective which are bloody, startlingly violent, unspeakably sad, and just plain confused. The sub-titling isn't bad but we needed to pause now and then to work out what was happening. However, for the majority of the movie we were carried along with the plot, entranced by the possibility that the detective might not actually be as mad as he seems. In some ways I was reminded of Angel Heart; another dark detective story poised on the edge of the unknown.
The special features were about average; the Q&A with the director would make more sense if you'd seen his other movies. We gave up halfway through the cast interviews as they weren't adding much to the overall experience.
So a film well worth renting if you like oddball mysteries. Not one to go for if you prefer high-kicking shoot-em-up action films. Definitely one to absorb and mull over.