Strangely compelling. The character, however underdeveloped he might be in this particular interpretation of the fiction, is enough to justify playing through what is otherwise a distinctly mediocre action title.
Constantine (the game) is terrible... In the early days of the PS2, Constantine would've been cutting-edge; a fun action romp. But this is 2005, not 2001. We demand that games look, sound, and play better than this.
No single aspect will blow you away, but there's enough variety, the puzzles are fun, the controls work well, and you keep moving quickly, so it's a fun ride that's unlikely to bore you unless you try to play through it a second time.