This is a concept of using a low cost cellphone or tablet computer as a book.
It can offer text, images, audio and video.
However, it is designed to be programed once and not changeable. It is a digital version of a printed book.
All radio transmitters are turned off on the device, so the use of the device is not traced.
It could contain a vast library of books. Hundreds or thousands of text only books or books with limited images can be stored on a device with only a few gigabytes of memory.
The obvious example is to store the Bible, Quran, and other sacred text in multiple languages. This would allow a reader time to examine what it true. The untraceability could be vital in many instances.
Write display driver.
Concepts maturing - resources lacking