Comics is the best app for buying comic books -- and graphic novels -- on your iPad. Well, that's not exactly true. Comics is one of the best places to buy comics, but the developer, comiXology also makes dedicated versions of the app for Marvel, DC, Dynamite, IDW, Image, and other publishers. They claim over 16,000 titles, more than enough to delight anyone's inner Sheldon. Comics itself has a great selection of titles from several of their partner publishers and, taken together, the comiXology apps are everything you need to get your weekly fix of new releases and classic back issues alike.
When you first load up Comics, or any of the dedicated comiXology apps, you're taken straight to the store and will have various options up top for featured titles, new or recently added title, popular or best-selling titles, and sometimes free titles as well. Browse your way through or use the tabs at the bottom to jump to series (like trade paperbacks, they're several issues collected into one easier-to-manage edition), story arcs (related issues you still have to buy and keep separately -- why not just make these into series, folks?), creators (if you're looking for specific titles by your favorite artist or writer), as well as the option to search, and My Comics/purchases to see what you've already bought.
There's a ton of content to be found. Comics proper has a good sampling of titles from the various publishers. The dedicated apps for Marvel, DC, et al have loads of current stuff, most of the popular arcs and series from the last few years, and a smattering of classics (though why I can only find something like Batman: Year One as a set of individual issues in a story arc and not as a collected series is irksome -- fix that DC!).
When you find something you like, just tap the price to buy, same as you would in iTunes, and the familiar in-app-purchasing system takes over. Your comic issue or collected edition is downloaded straight into the app and made available on your reading shelf.
Pricing is okay. Individual issues are often $1.99 though some newer/hotter titles are $2.99 which is too high. As Steve Jobs told the music industry a decade ago, their competition is free -- price things fairly and make them easily available and the market will flourish. Also, while Marvel offers true collections in their series, DC doesn't seem to have embraced that yet which is baffling. (Prices for the Marvel series range from $6.99 for smaller, more obscure 130 page collections all the way up to $24.99 for large, popular 330 page collections like Planet Hulk). There's also no subscription model, let alone all-you-can-eat offering.
The reading experience is excellent. Pages are shown one at a time, or side-by-side for double-page spreads. You can also double tap to "zoom in" and show only one panel at a time. There's no page flipping animation but swiping between pages is a breeze. You can also tap to bring up the controls which let you get info on the title, go to a thumbnail view of all pages, pull up the option for transition speed, letterboxing, etc. and get help on how the reader works.
You can't load your own comics, or comics you've bought in PDF form (for example, on Marvel's extensive DVD volumes), but that's what apps like Comic Zeal are for.
Overall comiXology has done an amazing job. Marvel, DC, and the other companies are also tepidly inching their way into digital confidence. It would be nice to have everything all in the Comics app and not need the separate Marvel, DC, et. al apps, for example (could you imagine if Warner, Sony, etc. were all separate iTunes app clones and we couldn't keep our music or movies in one place?). It would also be great to see the bigger collections, absolutes, omnibuses, etc. available, discounted the way they are for trade paperbacks in comic book specialty shops. (Speaking of which, the comiXology apps go out of their way to point out where you can go buy real-world paper versions of the comics, which is both awkward and charming.)
It's not quite iTunes for comic books yet, but Comics and the comiXology apps like Marvel and DC are getting terrifically close. If you're a general fan, get the Comics apps proper. If you're a Marvel or DC purest, get the dedicated Marvel or DC apps. If you love everything, get them all. With day-and-date new releases and an expanding back catalog of classic stories, Comics makes iPad the premiere device for any comic loving geek.