This is one of the all-time GBA classics! Even if you haven't been a fan of the Castlevania series (I wasn't) this game will captivate you like no other GBA game! This is my second favorite Game Boy game EVER (behind only Link's Awakening).
The graphics perfectly portray Dracula's castle; dark and dreary. The shading is perfect. Everything looks spectacular. A word of warning; the game is DARK! Make sure you play under a light or buy a wormlight (or substitute). The gameplay and story is what makes this game go. The game is different from most Castlevania games in that you receive experience from killing monsters and also that you will find items and be able to equip them to boost your stats.
You are able to cast magic spells using an innovative DSS card system (you'll find these in the form of drops from monsters).
The play control is fantastic; perhaps the best I've experienced for the GBA.
You owe it to yourself to try this game. You will love it!