E-Ink readers like the Nook touch currently come with 4 bit (16 levels) of gray, no camera, often no sound, no GSM, often no landscape detection sensor etc. And especially, the display refresh rate is very slow. Still or nonetheless they have advantages like battery time, especially with the display on, clear readability in bright direct sunlight over a tablet and display size over a phone and also more and more often come with Android. Here are some apps and hints which work great for that scenario.
Firstly, with the Kindle I had gotten used to using the great Instapaper service. Now with the Nook, there's no comfortable "Whispersync" to send documents to it via wifi. But if you root it, you can install instapaper apps, which are actually even more comfortable, have no limit to 20 articles, automatic syncing etc. My app of choice so far is EverPaper, which is specialized to saving notes to everpaper, but gets the pages for offlines reading from Instapaper.
For browsing, which is not great yet, because there's no page button scrolling as on the Kindle and the internal nook touch browser is very, very bad, I highly recommend the leightweight Opera Mini. Actually you can even use VNC clients and e.g. surf via your computer (remember to at least use the 8 bit color mode to save cpu power).
One of my favorite apps is also "Gespiegelt"/"Mirrored", which lets you access articles from the German Der Spiegel Magazine comfortably, although the font size is a bit small even in the largest setting for my taste.
Of course you can - which makes it really fun - read your ebooks bought at other ebook stores with Android apps, e.g. Amazon's Kindle app. You can transfer files with Dropbox.
And last but not least some games run great in this setting, e.g. the really fun strategy game Pirates and Traders or of course things such as Sudoko. The battery time is much better here, because there's no screen backlight to draw battery.
Conclusion: Many apps work great out of the box on eReaders. If you're a developer and you want to optimize your app for eReaders the most important thing is to have a switch to disable all animations to reduce flashing. Another option might be to use 16 levels of gray in processing, that could save some cpu cycles. And an offline mode will be much appreciated, because the wifi is one of the biggest battery drains on the long lasting eReaders.
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