Both companies are godawful at that, though. Hell, comics is the *only* type of publishing (except maybe tijuana bibles) that you can't find online at 3 dozen different retailers.
Here's an ISBN number of a comic trade, taken from Marvel's website: 9780785133797
Your challenge: Find a reputable retailer who sells it online.
Actually, I have to admit, I didn't expect to find *any* retailers selling it at all (I did the same search about a month ago with no results), so the fact that there's currently one surprises me. But why isn't Amazon on the list? Why not Barnes and Noble? Hell, why doesn't Marvel's OWN WEBSITE (the one I got the ISBN from) show up?