I actually played this shortly after the translation was released ('Oh! This guy plays game that have drawings of boobs in them! GET HIM!').. I'll throw my two cents in.
It's a visual novel revolving around vampires and some other supernatural stuff. That means you read a lot, vampires kill some people, some vampires get killed in return, and you occasionally get the chance to choose between several different options that influence how the story will unfold.
So, basically the 'gameplay' offered is little more than a 'Choose Your Own Adventure' book, with some choices leading to good ends, some bad, others instant doom. The artwork isn't the greatest by any stretch of the imagination, and whatever sound/music involved wasn't worth me remembering. As a result, that 'Lets Play' link mentioned earlier is actually a great alternative to actually downloading, installing, and playing the game (Which takes about 15 or so hours to see all the endings, by my guess).
As exciting as that sounds.. Tsukihime is actually one of the better visual novel games released, as it offers a pretty good story filled with some interesting characters, especially compared to other adult oriented games in the visual novel genre which are generally little more than sex romps.
If I remember correctly, the translation patch (Which is fan made, but is easily professional quality) actually has the option to remove all of the sexually explicit scenes (There's only a handful of them) from the game, which just goes to show that there is an actual story in there that some people consider to be worth reading on it's own.. In fact, the game has actually expanded out into other games, manga, and an animated tv series.
The violence as I recall isn't terribly graphic.. I actually don't remember any horribly violent images in the game (I think there's a scene with a few dead bodies and some blood.. Barely R-rated gore, if that), and the OP's text is easily the most graphic scene in the game, and it's SUPPOSED to be that way. I don't want to throw spoilers into it, but that scene is really supposed to come across as being a horribly violent, barbaric, savage, and cruel. It's supposed to be an uncomfortable scene. It really wouldn't work any other way.
All in all.. Is it a mind shattering, award-worthy tale? Not really.. But it's worth a look. I recommend it if you're interested, provided you're old enough to handle adult content and can muster up the strength to stomach a few drawings of naked ladies. It's hardly the 'butcher people while they're still alive while having sex with nuns atop a pile of rotting corpses' game that some people seem to think it is.
Hell, I think some of the Conan books are more graphic than this game..