There's this great website/app I buy them on, which allows me to buy them and download them to my phone and computer, and read them whenever I want. It's always very high quality, and there are sales more often then not. I bought the entire crisis on infinite Earth's series not too long ago, for like 6$.
There's also a plethora of manga, illustrated novels, etc.
The app is called "Comixology", and it's free to make an account, and download the app to your smart-phone, and there are even some things on there for free, occasionally. I definitely recommend checking it out.
I know that some people prefer to have actual copies, but this is the best option in my opinion, since you don't have to worry about them getting damaged, being lost in shipping, being the wrong thing you ordered, and the most common problem I used to face, which is that most comic stores never have the issues I want. This app though has pretty much all of them. It's got damn near any manga you can think of, including Naruto, DBZ, etc, and it's got just as many of Marvel comics, including things like the X-men series, Daredevil, Spiderman, and DC comics, like COIE's, Infinite crisis, Superman, Batman, The Sinestro corps war, and several other major story arcs, including the entirety of ALL issues, including side-stories and extra's, of the Blackest Night.