The world of Marvel Comics is on iOS.
First things first, this is an official Marvel Comics app, so you'll definitely only be able to read and buy their comics. But as long as it's Spiderman you like and not Batman, Marvel Comics is a superb reader.
Marvel Comics is free to download, and features some free content, but it's really designed as a portal to buy and download comics. You can't import CBR of image files of scanned comics, and everything has to be downloaded and bought within the app. This means you can't share your comics like you might have when you were a kid, but once you've used it, you might not care.
Viewing comics in Marvel Comics is absolutely fantastic. You can browse with a cover flow-style page viewer, then view full screen pages, and pinch and zoom quickly and easily to move around a page.
The really great feature, however, is the animated panel transition. Swipe right to left on a page and it isolates and zooms to the first panel, swiping again slides to the next, or sometimes to another part of the panel when it's particularly big. This is incredibly smooth, user friendly and feels great. It's not unique to Marvel Comics, but that doesn't make it any less cool.
Some fans will never read a comic digitally, but for those who do, this Marvel Comics app makes the touch screen experience really work well