For those who don't like to read manga on their computer, and can't afford an iPad or iPhone, Viz has a third way to read manga digitally: On Barnes and Noble's Nook Color and Nook Tablet e-readers. The Nook is smaller than the iPad, but it is also less expensive: The Nook Color is currently on sale for $199, and the Nook Tablet is $249. If you don't mind the smaller page size and the lack of free samples, this is a pleasant way to read manga digitally without breaking the bank.
At 5" x 8", the Nook is just a little bit taller than a volume of manga. Open it up, though, and you will see that the screen is smaller, and in fact, the reading area for manga is only 3½" x 5¼". That's small. The images and lettering are sharp enough that I didn't have much trouble reading it, but your mileage may vary. The Nook has pinch and zoom functions; moving your fingers apart on the touch screen will enlarge the image, and you can move from place to place by dragging your finger across the screen. When you turn the page, though, the next image will be the default (small) size. The pinch and zoom on the Nook are a bit jerkier than the iPad but still quite tolerable.
Like the iPad, the Nook has a landscape mode; turn the device on its side and you can read two-page spreads. The pages are obviously quite small at this point, but still readable. All the manga I sampled on the Nook had a creamy white background color, which was a little easier on the eyes than the colder backlighting of the iPad.
Navigation is straightforward: The Nook has an "n"-shaped button at the bottom center of the frame that brings up a horizontal menu with a home page, library, search, and other choices. The library page is simply a bookshelf displaying the covers of all the books; tap one to open the book. The Nook can handle the right-to-left orientation of manga just fine, and swiping turns the pages smoothly in either direction. Tapping the top or bottom center of the page brings up thumbnails and a slider that let you move from place to place in the book, as well as buttons for a table of contents and brightness control.
In terms of selection, Viz has done a good job of pushing its books into the Nook store; there are over 600 volumes available, including recent volumes of top series such as Naruto and Bleach, old favorites such as Backstage Prince and Absolute Boyfriend, and some more literary titles like Natsume Ono's not simple and the charming sci-fi tale Saturn Apartments. The manga is priced at $4.99 per volume, the same as on the Vizmanga.com website and Viz's iOS apps.
Two things are missing, though: The free sample chapters and Shonen Jump Alpha. The Vizmanga.com website and the Viz iOS apps offer the first chapter of every series (usually about 60 pages) for free. The Nook Store does have free samples, accessible from both the Barnes & Noble website and the Nook, but they aren't as generous. Viz's digital magazine Shonen Jump Alpha is not available for the Nook Tablet, although many individual volumes of Shonen Jump manga are available. The Nook also doesn't sync with the apps and the store, so if you bought digital manga in one of those venues, you will have to buy it again for the Nook.
Overall, though, the Nook is a reasonable alternative to the iPad, and if you have one anyway, it's worth taking a look at Viz's manga selection.
(Disclosure: Viz lent me a Nook Tablet for this review, and I compared it with the Viz app on my own first-generation iPad.)