You can never get enough action in an anime...or at least, that's my opinion. Basilisk is essentially Naruto, except it's much darker, doesn't involve annoying kid ninjas who spout the same 4 lines over and over, and is set in Japanese history. Oh, and did I mention there's lots of action?
The best thing about Basilisk, has to be its ample use of cool ninja fighting. The story behind all this fighting is somewhat generic, but its passable I suppose...anyway, it's all about the fight sequences.
Basically, two ninja clans with a deeply-embedded hatred for one another are trying to kill each other off. Why? Basically because they can. There's very little nonsense, and each episode is filled with...you guessed it. lots of action.
Where Basilisk falls short is with its characters... Unlike Trinity Blood, where the characters are just annoying, Basilisk has several very interesting characters, all of them ninja, each with their own special ability. Unfortunately, you're never given a chance to really connect with these characters, because I can guarantee that at least one major character dies every one or two episodes or so. And since there's only around 20 of them or so, and there's already been 14-15 episodes...you can imagine that there's not many of the original cast that's made it this far.
So basically it comes down to the fighting. And it is cool. And that's good enough for me.