A solid attempt at a 3D Castlevania that is unfortunately marred by some noticable flaws. Recommended.
The Gameplay is pretty solid and relies heavily on old-school NES style Castlevania gameplay mechanics. A plus here is that you can play as two pretty different characters - Reinhardt and Carrie. As Reinhardt you've got your whip, your melee sword (a great addition) and some items you can pick up and upgrade slightly including axes, throwing knives, crosses and holy water. As Carrie you are a magic user and you use long-range tactics against your enemies. Aside from attack elements, they also differ in that each one plays 2 different stages than the other. For example, Carrie can play Tower of Sorcery but Reinhardt can't. Reinhardt can play the Tower of Execution and Carrie can't, and so on. The platforming elements are reasonably solid, although jumping can be annoying as the animations and collision detections aren't as solid as, say, Mario 64. The controls are basically average, but they are still fun. The camera is usually stable but can be a problem in several portions of the game, most importantly while trying to overcome jumping obstacles (sometimes you can't even see where you're jumping to). This is a noticable hiccup in an anotherwise sound system. The game is reasonably difficult even for experienced gamers, and this helps the playability tremendously. This is definitely not an easy game, especially on hard. The boss battles are usually pretty memorable, especially the fight against Death which, so far, is the best one in the series. You'll see when you get there.
The graphics are pretty good for an old N64 game, and although they aren't as great as Ocarina of Time or even Mario 64, they still feel right for the setting. They are bleak and somewhat depressing, even eerie when appropriate. They essentially capture the moods effectively even though they could've been a bit more stylish. The characters aren't that great design-wise, although they aren't bad either. They're distinctive enough not to be carbon copies of other game characters, but they aren't as good as, say, Alucard from Symphony of the Night.
The music is another strong point in the game. It has the second best Castlevania score (second only to Symphony of the Night) with very memorable pieces including the Tower of Execution theme and the Tower of Sorcery theme. They just sound completely appropriate for their various settings, and it's unfortunate that you can't buy the soundtrack for the game as it would be a good one to acquire. The sound affects are also surprisingly well done, especially the whip, item and walking effects (walking on the concrete sounds really good for some reason. You usually wouldn't think something like that would even be noticable, but it is here).
The story is cliche for the series, as Dracula's castle has come back 100 years since it's last appearance as per usual. It's a bit of a letdown, considering Symphony of the Night's presentation and relatively interesting story (although to be fair, even that game didn't have THAT much in the way of story, either), but not a huge detriment. Essentially you are invading Dracula's castle to put him down for another 100 years. Playing as either character gives you different endings, and you also get different ones depending on how long it takes you to beat it. They aren't that amazingly different, but it adds to replayability.
All in all this is a solid Castlevania game that plays well and is a fun and challenging experience. It has some weak elements, yes, but overall it's a very good game. It's not necessarily a classic, but you won't be disappointed with it. For fans of the series this is definitely worthy of checking out.