I wonder how many good things can I say about xxxHolic while holding my breath. Short answer: so many that I wouldn't be able to finish due to a little conditon called asphyxiation. xxxHolic is wonderful. Just truly wonderful. I haven't read such a great manga in quite a while.
First off, the story. The story is excellent, though it can be confusing at times. It takes the structure of having a main plot they introduce at first, and a later plot they only allude to at the beginning. It then takes both plots, and switches them around constantly, without warning, and....I can't think of another way to describe it. The ending is satisfying and has a nice little reveal to it. Since this series does a crossover with another series, it does make it a rather interesting to see how both plots meet and intertwine.
I would recommend this series for anyone who likes.....well Hell, anyone!