It's best to know the story of "Hamlet" before you watch this film, since if you don't, you may be confused by the fact that, this being a reimagining of "Hamlet" from the perspectives of two minor characters, the main characters from Shakespeare's play only interact with our two anti-heroes in the few scenes in which they're part of the official version of the play, and since they're not present to witness most of the important events that motivate everyone else, we don't see them either.
On the plus side, if you like intellectual comedy, this is funny in a very clever way, though not exactly laugh-out-loud hilarious, and a young not-yet-A-list Gary Oldman is great fun as the smarter of the pair (even they can't always remember which is which), and makes you wish he'd made more comedies. The somewhat forbidding Tim Roth, however, seems a rather odd bit of casting.
Unfortunately, there are too many scenes that feel exactly like a stage-play made into a film, probably because that's what this is. And letting the author of the play direct the film - it's the only movie Tom Stoppard has directed - wasn't such a great idea, since Stoppard seems to have little grasp of cinematic technique. He doesn't properly appreciate that, while audiences will accept very basic scenery on stage, in a film, it helps if you can really believe that you're in a castle or on a ship. It's a pity the proposed movie directed by John Boorman fell through - I'd love to have seen this done in the style of "Excalibur"!
The basic premise of fictional characters gradually becoming more and more aware that they're helpless to control their destiny, and what's more, there's something badly wrong with reality, is interesting, but visual aspects of this that ought to work very well on film, such as their inability to comprehend scene-changes that suddenly place them in a new location, are handled in an oddly unvisual and rather flat way. Ultimately this is little more than a play with a camera pointed at it. However, it's a very good play if you like that sort of thing. And Gary Oldman's excellent.
I am afraid I switched off half way through I couldn't follow it at all, I don't know the Hamlet story and I guess it may be easier to watch if you know Hamlet
This film is already excellently reviewed by Count Otto Black above so all I have to add is that I found the wordplay and both leads mastery of the material very engaging. The comedy, such as it is, won't make you laugh out loud but I smiled pretty much the whole way through the film.
Some standouts were the scene where the leads meet the theatre troupe for the first time which I immediately went back to after finishing the film and the scene where Tim Roth is watching the troupe performing in the castle for the hoi polloi. In a film that concentrates so much on the verbal sparring and jousting between it's characters, it's satisfying to think of the positives of the physical aspects of the two aforementioned scenes.
The character of Hamlet was another highlight and probably testament to the strength of the source material that watching his performance makes me want to read Hamlet again after decades!