Because MegaReader, you see, supplies enough reading material to last a lifetime. The app promises access to a whopping 1.8 million free e-books--far more than any other reader app I know.
Whether that count is accurate is difficult to say, but at the very least you'll have enough books to tide you over until rescue comes--or you get mixed up with The Others.
The app comes with 22 books preloaded, all classics like "A Tale of Two Cities," "Pride and Prejudice," "The Call of the Wild," and "The Art of War."
To get more, tap Download Books, then choose from half a dozen online sources of free titles: Baen Books, eBook Search, Feedbooks, Internet Archive, Project Gutenberg, and Smashwords.
Obviously you won't find any Stephen King or Toni Morrison among these listings; everything is strictly public domain (or free from the publisher). Though there are plenty of modern titles in the mix, they're almost certainly from authors you've never heard of.
That's not necessarily a bad thing; it's just something to be aware of. The MegaReader app itself is on par with others I've used, with plenty of customization options for things like font style and size, background color, line spacing, and text justification. And although it's not optimized for the iPad, text looked plenty sharp and readable even when zoomed.
The catch, of course, is that you need an Internet connection to download books--it's not like the app comes with all 1.8 million installed. As long as you plan ahead (i.e. download what you want before you crash on the island--because, let's face it, it won't have 3G, or even Wi-Fi), you'll be fine.
MegaReader costs $1.99. If there's an app that offers more e-book bang for the buck, I haven't found it.