Kindle users can now lose themselves in the worlds of Zork I, II & III, as long as the connectivity lasts, and not in the dark obviously.
The capability isn't actually new, PortableQuest.com has been providing a minimal interface for those who fancy seeing spending some time in a maze of twisty little passages, via their cellphone, but now there's an even-more-minimalist version aimed specifically at Kindle users.
Zork was one of the first text-based adventures, spawning a legacy that led to generations of gamers screaming "pick up the bloody thing" while trying to guess the exact phrase required to complete the desired action. But it has also been hugely popular in its time and worth revisiting if only to remind one how far we've come.
Even more popular than Zork, and equally text-based, was The Hitchhikers Guide To The Galaxy, despite (or because) most of us never made it to the pub. That's available in Java form, and Flash, but not yet in the minimalist HTML interface suitable for rendering on an electronic book - even one that happens to have a keyboard.