Nintendo pulls as much paper as they can out of their manuals these days, but all those pretty pictures and fat infos have got to end up somewhere. And somewhere they have landed indeed! Hit the Home button on your GamePad while playing a game, tap the "Manual" button, and voilà.
The Wii U manuals are actually extremely similar to the 3DS ones, which themselves were incubated on DSiWare titles. These Wii U ones though are much better replacements for proper paper manuals than the 3DS ones have manged to be. Aside from the obvious benefits you get from a gigantic pixel-rich screen, the individual manual pages can now support background images and footer art, like with Nintendo Land as seen above, a nice upgrade over the solid-colored 3DS pages. There's a lot more opportunity for design here, and lots of pages feature nice big graphics. (Correction: as Tyeforce points out in the comments, select 3DS titles do indeed support background images.)
The real benefit of a digital manual is that you can interact with it, though. The 3DS manual pages are pretty much static, barring a font-size option. The Wii U manuals introduce two varieties of shortcut links—little numbers attached to screenshots that scroll you down the page to explain what the number was pointing at (and then back up if you tap the number again), and page number navigation links that move your forward or backwards to a related subject.
And here's a neat little thing: the game's model number is at the bottom of the manual table of contents. AWESOME!
Check back tomorrow for another unbelievable Wii U secret!