Who knew iTunes had such a long tail?

This morning, Stock Advisor recommendation Marvel Entertainment (NYSE:MVL) unveiled its own digital comic library. In many ways, Marvel's move aped the iconic online media store, which has helped Apple (NASDAQ:AAPL) sell millions of iGadgets.

I know, the iTunes comparison isn't perfect. Apple doesn't own content like Marvel does. It's a reseller, more closely resembling competing offerings from Amazon.com and Wal-Mart.

Digital Comics Unlimited (DCU), as Marvel is calling the service -- perhaps as a dig at rival DC Comics? -- has a handful of community components to enhance users' experience, including personal reading lists and rating features. DCU is only available via a $4.99- or $9.99-per-month subscription, which lets users read 2,500 classic and recent comic books via their Web browsers. Editors plan to boost that total by at least 20 new titles per week, although the very latest titles won't appear until months after they've hit newsstands and comic shops.

In all, DCU is much more like Napster (NASDAQ:NAPS) or RealNetworks' (NASDAQ:RNWK) Rhapsody than what iTunes offers. Regardless, none of these firms would be in the digital distribution business without Apple. Nor would Viacom (NYSE:VIA), General Electric's (NYSE:GE) NBC, or Disney (NYSE:DIS), all of which either have sold or still sell content via iTunes.

The model's been proven successful. Now Marvel hopes to copy it.

But let's be fair about what that means. Having DCU probably won't do much for revenue. Operating income and cash flow could enjoy a modest boost, however. Think about it; Marvel's sole cost for previously published editions would be royalties, hypothetically.

Aside from occasional reprint volumes, there's been virtually no other way for Marvel to make money from the August 1962 first appearance of Spider-Man in Amazing Fantasy #15. Until now.

We don't yet know how comics fans will react to the new digital Marvel. Oh, wait -- actually, we do. Quoting from Marvel's page for DCU earlier today:

Hey, True Believers, the response to Marvel Digital Comics Unlimited has been so overwhelming, we're just doing a bit of routine maintenance to make sure you have a great experience! We'll be back shortly. Thank you, Marvel.com.

Face front, Fool. Marvel's digital days are just beginning.

Zowie! Another pulse-pounding dose of related Foolishness awaits:

Marvel is one of the best stocks ever to enter the Stock Advisor portfolio. Get a 30-day free pass to the service to find out how David and Tom Gardner have engineered a 41-point drubbing of the S&P 500 over the past five years. There's no obligation to subscribe.

Fool contributor Tim Beyers wonders whether you're a Marvel or a DC. He owned more than 2,000 comic books, as well as shares and LEAP options in Marvel, at the time of publication. Amazon and Marvel are Stock Advisor selections. Wal-Mart is an Inside Value pick. The Motley Fool's disclosure policy could swear that it saw Cap hanging out by the local VFW last night.