I only buy trades from Amazon.com. The only place I could buy comics at retail is a local Books-a-Million and I hate that place. They are WAY overpriced and want you to buy a $20 membership card just so you can get 10% off their merchandise. Screw that.
I currently own Vol. 1 - 3 of this. I plan on getting the other 3 before the movie is out. But I'll agree, it's kind of a hard read if your not into the goofiness of anime or if you take your comics very seriously. The comic also seems to be all over place with random flashbacks that come out of nowhere and how fast the plot moves. But it gets better as it goes on and I don't regret reading it and I think that the fact that I want the last 3 volumes says something.