xxxHolic may well not appeal to those who prefer their anime to be of the blood and darkness variety. However for those susceptible to stylish artwork and intelligent, if somewhat metaphysical, dialogue and plot, it has much to offer.
The artwork is noticeably different from most anime, which is refreshing; the characters in particular having a stark art-deco feel reminiscent of Aubrey Beardsley's drawings. The production as a whole is not stark however, and although colour is used with discrimination, when it is used it is drawn from a beautifully matched colour palette. Also quite striking is the clothing - some of Yuko's dresses are particularly fine. Clearly the quality of the art is significantly important to someone in Kodansha or Ayakashi Workshop - although undoubtedly driven initially by Clamp's artistic vision. This is not to say that xxxHolic doesn't also possess many more familiar anime characteristics. There are monsters, and encounters with magical beings from Japanese mythology, but they are often tenuous and suggestive of evil rather than visually grotesque, or, as in the latter case, morally ambiguous. More often than not they are present to illustrate a moral point rather than to tear you limb from limb.
While the plot is of the fairly anime-typical metaphysical/occult variety, I found it quite compelling, aided by a sharp and witty dialogue - although I have not listened to the dubbed version; the Japanese actors' voices and inflections being, in my experience, too important to miss. Also in common with numerous other anime productions is the frequent reference to ethics, moral dilemmas and their repercussions, and the spiritual consequences of thought and behaviour. Lacking the gore often used to counterbalance this tendency (cf `Elfen Lied', `Claymore' etc.,) some Western viewers might find xxxHolic too idealistic, irritating, or simply so much nonsense - personally I found it fascinating, and felt as if I was being offered another glimpse of Japanese culture. For those who prefer their entertainment to be more visceral, be warned - death and destruction take a back seat here, and even terror (when it occurs) is dealt with in a decidedly cerebral way.
According to Wikipaedia, Kodansha's motto translates as `To be interesting and beneficial' - a phrase which could be applied very suitably to xxxHolic.