Let’s assume for the time being that “Constantine” was not based on a comic book. Let’s assume that there is no such thing as “Hellblazer,” a DC/Vertigo comic about a man who fights for neither hell nor heaven, but to protect mankind from both. Let’s pretend that “Constantine” stands alone.

With that assumption in place, “Constantine” is a decent movie. It’s not excellent by any stretch of the imagination, but it’s not terrible either. As a paranormal thriller with a religious twist, it accomplishes what it sets out to do. You can’t ask for much more than that.

“Constantine” tells the story of John Constantine (Keanu Reeves), a chain-smoking supernatural investigator who can see the demons and angels who live amongst us, influencing our everyday lives. When police detective Angela Dodson (Rachel Weisz) asks him to investigate the mysterious death of her twin sister, they uncover a plot that could turn the mortal world into a living hell. It’s up to John Constantine to battle demons within and without to overcome the dark forces that set the plot in motion.

The movie is drenched with visual style. The world around Constantine seems drab and used-up, like something has drained away the world’s vitality and left behind nothing but a dried-out husk. It seems fitting, considering the mood and themes of the film itself.

Reeves did a satisfactory job as the title character, mostly because his character is quiet and brooding, something that doesn’t require much acting. Let’s face it: Reeves has a pretty limited range as an actor. It seems that in this instance, Reeves has been matched with a character that fits comfortably within his range. So no complaints there.

I will confess, I have never read the comic book upon which “Constantine” was based. I’m sure that I would enjoy it if I had the chance, but that’s beside the point. However, everyone I talk to who has read the comic has told me that “Constantine” is a terrible adaptation of the source material. Apparently, they changed the characters too much (particularly in John Constantine’s case), altering entire motivations and changing the characters into something completely unlike their comic book counterparts.

In conclusion: “Constantine” is a fun little popcorn movie that is worth watching once or twice and then forgetting. While it fails as an adaptation, it nonetheless succeeds in being interesting enough to keep you interested for two hours.