I think the final confrontation with the final villain of the anime was kinda anticlimatic. I mean, you had him taunting Alice and going on about being so much smarter etc etc...
...and then you find he's ODing in his hideout. What.
That said, it was entertaining, and I liked the OP and Alice. But it's overall not quite a series that has caught my fancy and remained in my mind.
...can still sing the OP from memory though.
With the key transposed into the range a tenor could sing.