Although it's my least favorite Castlevania from the GBA era, it's still a pretty decent game.
This was a launch title for the GBA so you can't expect the graphics to be amazing, but the monsters could've been varied a little more and the game could've been a little brighter. But the dark screen isn't nearly as bad as the lack of monsters. Although there are quite a few different enimies to slay in the game, you will notice they are mostly different versions of "skeletons" and "armours," which was a huge dissapointment.
The sound in the game is sub-par of the great Castlevania sound tracks, but it's still good enough to go along with the eerie setting of the dark castle.
What I was most dissapointed with was the DSS card system. There was no point to it, because there were only a few cards to choose from, only certain ones matched up right, and it was hard to get the cards. Although the cards did give a changed look and power to the whip, they didn't help that much and got boring to use.
Although I found a lot to dislike in this game, I still enjoyed it because, well, it is a Castlevania game. So if you're a fan of the series, or would like to play a classic, but hard, action adventure type game, Castlevania: Circle of the Moon is worth checking out.