I installed a reader with a Wikipedia dump (without multimedia) on the original iPhone. At the time (at least in my region) WiFi was quite rare and it really did feel like the Hitchhiker's guide and incredibly powerful.
I only kept it for a few weeks though since it consumed almost all of the space. (And I imagine it was probably my language mutation, the english Wikipedia must have been too big already.)
I'm not trying to kill the fun here, but since this thing relies on a working internet connection, it would probably be pretty useless on a remote island