I just completed volume 14, which is the final volume. I felt a tinge of melancholy afterwards, similar to the feeling you have after a long vacation. There is sadness in seeing it end, yet gladness that I experienced it and happiness to have a conclusion. After 12 long years of writing, this series has come to an end. The author/illustrator mentions this in one of her numerous sidebars. She states that people were constantly writing or emailing her, eager to know when the next installment would be released, and she felt terrible that she couldn't write them sooner. When you consider it, there were 14 volumes over 12 years. That's less than one per year! You wouldn't think much of that if it were a novelist, but she also has to illustrate everything! Nevertheless, I'm glad that I only had to wait a short while because: 1) I hadn't heard of this series until about a year ago and 2) I'm not Japanese, so I only have to wait for the time it takes for the English translation to come out.
The ending of the book gets a bit strange with a lot of talk about light and dark, but it's still very sweet, aside from the people who are killed or have "evil bits" (my term, not theirs) oozing out of them. It ended very neatly, with every character being accounted for.
Read it!