So I went through this strange shounen-ai period for a while, I blame 4chan and teenage sexual confusion. Also having no straight friends, but I don't really blame them. I think I have the first 6 volumes of this series. The only other manga I actually own are the 2 FLCL volumes, so I hope this says a lot. I only buy a manga when the art and the story completely blow me away, which they did in this, utterly, when I first read it. A friend lent it to me, but a few pages in I thought "I MUST POSSESS THIS" so I bought it and continued to buy new volumes when they come out. The amazingness has kind of lessened in the later volumes, possibly because the story isn't really going anywhere, possibly because I've lost all interest in shounen-ai and find the college student & 12 year old boy dynamic mildly creepy.
In short, it was the art (and amazing binding! well done tokyopop) that drew me to actually purchase this series. It's the best I've seen in such a long running series. Don't take my recommendation too lightly just because you don't like the "messy" style of FLCL that I mentioned above. This has a much wider appeal.