Hey... if you watch xxxholic they make an anime appearance at the beginning of episode 6. ^_^ My jaw dropped open and I got so excited cuz I thought I'd never hear about it again. ><;; So yeah.. I'm taking it that CLAMP are trying to get more publicity for the series (I'm rooting for them) and that... it's set in the same world. =D which makes sense! The theme's very similar to XXXholic.
I've got the first 3 volumes.... it's definitely got the CLAMP essence so if you're a fan of them you'll definitely like it. I even got a friend of mine who's not really into manga/anime to read it.
Out of all the CLAMPs I've read so far this one has more shonen ai teasing (but it isn't shonen ai... Kazahaya just gets teased a lot.) Heaps of the wall art I think is definitely targeted to shonen ai fans. So if you're a fan of SA you might dig this... and if you're not, then you have nothing to really worry about. ^^;;