Books made out of paper and leather are so last millennium. Stalwarts of the digital age are clamoring to replace them with handheld digital libraries. Potential new-age book readers include the Apple (Nasdaq: AAPL) iPad, (Nasdaq: AMZN) Kindle, Sony (NYSE: SNE) Reader Digital Book, Barnes & Noble (NYSE: BKS) Nook -- and on and on in an onrushing flood of options. But one fresh entrant into the e-book market comes with an unbeatable installed user base.

Video game veteran Nintendo (Pink Sheets: NTDOY.PK) is set to launch a selection of 100 classic works of literature for the DS handheld gaming system -- along with a new DS model with a significantly larger screen.

Not impressed yet? Consider that there are more than 120 million DS units in use today, then sit down and figure out how long it'll take for Apple to sell that many iPads. I don't think it'll happen -- ever. And each one of those DS systems now becomes a potential e-book reader. If this test catches on, there's no reason why Nintendo wouldn't extend the concept with pay-per-download content, a series of packaged compilations like this first one, and more. Every DS comes with Wi-Fi networking installed, and the timing of a big-screen version next to this book-reading product tells me that Nintendo is thinking hard about this opportunity.

Company spokeswoman Cammie Dunaway doesn't exactly confirm that thesis, of course. "It’s just one more way to enjoy your device," she told a BusinessWeek reporter. The lady doth protest too much, methinks. 

Nintendo's genius doesn't lie in wowing consumers with high-tech wizardry like Apple does, but the company is great at putting workable solutions into the hands of willing users. The DSi XL may not be the perfect platform for reading a book, but it's good enough if you don't have anything better at hand. Plus, it's a multipurpose device that kids like to keep close at hand. Convenience is still king, you know.

So watch out, Amazon. Back off, Apple. Mario and Luigi are invading your territory, and you have to take them seriously.

Would you read "Moby-Dick" on a portable media reader -- and which one would you choose? Discuss in the comments below, Captain Ahab.

Fool contributor Anders Bylund holds no position in any of the companies discussed here, but his kids have two DS systems and one DSi between them. Apple, Amazon, and Nintendo are all Motley Fool Stock Advisor picks. Try any of our Foolish newsletters today, free for 30 days. You can check out Anders' holdings and a concise bio if you like. The Motley Fool is investors writing for investors.