You can view the full archive of all the comics, which will automatically fetch the comics so you're always up-to-date. Found a comic you really love? Well, with xkcd viewer you can favourite comics you like, and view them through the Favourites page for quicker viewing!
You can scan through the comics, even jumping to the very first to the very last, as well as randomly jumping through them, too!
Everything is cached, so the app is not constantly fetching from the Internet - of which you can clear the cache from within the app.