Remember when we (that is, the "we" who allowed ourselves to get caught up in the hype) briefly thought the monster in Cloverfield was a lion? This arose because one of the beautiful people in the mind-blowing trailer actually shouted, "It's alive!" but at that stage, in the confusion, all we had to go on was a big distant roar, and the misheard "It's a lion!" seemed significant. Like a lot of people, I went to see the film over the weekend, which, at 84 minutes, is not so much longer than the trailer - and something of a relief in this age when 158 minutes is the new 140 minutes (There Will Be Blood, American Gangster, Lust, Caution etc.). If you haven't yet seen it, that may be because it keeps being described as "Godzilla meets The Blair Witch Project", which, I can attest, just about covers it. If this does not appeal because Blair Witch made you feel a bit nauseous with its constant hand-held camcorder verite, stay away from the cinema!

If it's because you thought Blair Witch did not live up to its hype, likewise. (I think it did, incidentally.) Although I will say that Cloverfield takes the same technique to a new level. While Blair Witch was ultra-low budget, this one - which does, after all, depict the destruction of Manhattan by a 500-foot not-lion - cost $30 million (Blair Witch cost $60,000). The hand-held, mobile-phone/YouTube style is key to the narrative, and to the "it's-really-happening" immediacy, but it's also an illusion. As the monster marauds, we see glimpses of it on the camcorder as our good-looking heroes run for their lives. This is a really clever way of saving up the "reveal" for later, as in so many of the best monster movies. You find yourself arching your neck and being grateful for any tantalising peek of a leg or tail as the camera bumps along. This is pretty clever. But although you're ostensibly seeing what they see, you're actually seeing some fairly sophisticated digital special effects fed through the home-video lens. A gigantic sleight of hand, or mouse. It feels chaotic and random, but is in fact very brilliantly directed by a man called Matt Reeves (who wrote The Yards and Under Siege 2, and directed some telly programmes we haven't seen).

Cloverfield is a thrill ride. It's not actually frightening as such, or at least, it is at the beginning when it feels like September 11 is happening right before your eyes, but it is tense, and it does have high-wire disaster movie set-pieces, which appeal to me greatly. Here's a monster movie in which nothing is explained - you're as in the dark as the occasional shots of newsreaders on TV screens and the running, screaming, looting Manhattanites - and no context is given. Nor is it explained why the film is called that, although we know that it's the name of the street that producer JJ Abrams' office is on.

As we left the cinema on Saturday night, one girl said to her boyfriend/husband, "That's the last time I let you choose the film." Make of that what you will. I wish it had been a giant lion, though.