Initially, and this was years ago (geeze, probably about four years ago now) I started reading Tsubasa: Reservoir Chronicles but didn't start reading xxxHolic until things started getting confusing in TRC. I ended up enjoying Holic more, probably because it had a less confusing plot line, but now that the series is done I'm really not sure what to think about it. Sure I enjoyed a lot of the series but at the same time it had quite a few issues as well.
xxxHolic by CLAMP
Summary: Watanuki not only has the ability to see ghosts, spirits, and other things that regular humans cannot but they are also attracted to his blood and try to eat him a regular basis. He impulsively wishes once that this would stop happening and happens to say this in front of Yuuko, a shopkeeper whose store grants wishes. Ever since he's been doing errands and chores for her to work off his debt and meeting a truly wide variety of humans and yokai.
The Good: Despite what I say below, xxxHolic did have a stronger ending than TRC did (that's a pretty low bar though). I loved the series when it was either standalone chapters or short arcs that showed strange situations and the characters growing up. Plus, I love stories containing spirits and other beasties (as long it doesn't involve a lot of romance mind you) and xxxHolic kept me perfectly satisfied in that respect. Some of the smaller crossovers with TRC did work well (I loved the crossovers in the early days where you would just see items passed between the worlds) and I really want to see someone else pull off the crossover series trick, just with a bit more planning please.
The Bad: I'm reviewing xxxHolic and xxxHolic Rou here and I don't think that Rou was even needed. If the story had actually done something with the plot that wouldn't be the case but there is no change in Watanuki between the end of Rou and the regular series. I'm still annoyed that CLAMP wasted a good opportunity to tie up some of TRC's plot threads* and really, only one of the characters got a good wrap up. xxxHolic was at it's strongest when it only had minimal crossover with TRC because once that series got crazy xxxHolic stopped making a lot of sense as well.
The Art: The art doesn't translate well to animation but as stills it's gorgeous art. This was during CLAMP's streched out people period and their art looks way better than that style should. Each chapter page and cover illustration is meticulously detailed and the artbook spreads will cause enterprising cosplayers to tear their hair out for generations to come. Again, the art didn't translate so well to the anime (hence why I haven't seen much of it) but in still form, once you get used to it, the art fits the series perfectly.
This is a story I want to own someday, and in print too, but I might just hold off buying the Rou part for a long time. Now, I wonder if there are any artbooks for this released stateside....
*Apparently both stories got away from them and ran for much longer than they planned, I know a few members of the group said they needed to re-read Holic to get the ending, never a good sign if you're the co-creator.