It's a very solid Castlevania game that takes liberties with the story (in fact it's still screwing with the timeline). The soundtrack is Michiru Yamane's first work with the Castlevania series, and even then her stuff was amazing (Sinking Old Sanctuary and Calling From Heaven got their starts here). The graphics use the Genesis' effects well, with 3D pans, segmented sprites and even water reflections. The palette and stage designs are weird and dark.
The map take you around the world to various countries. Set in the World-war 1 period, the mood of the game is a little on the creepy side, but with a good amount of that weird Konami quirkiness thrown in (especially the Munitions Factory). Overall the levels are very well varied and none seem out of place.
There's new sub-weapons like Batarang-style projectiles and there's two playable characters who play very different. You'll want to go through with both as certain characters can only access certain areas and secrets.
The Genesis was never good with sounds, though, and the sound effects are easily the weakest part of the presentation.
So yeah.... it's a great game, but it's definitely got its own feel. It's a must play if you're a CV fan. Afterall, IGA's next move with the plot will determine just how Bloodlines fits into the whole picture. And it's 'bout time it's explained.