Where have you seen that advertising? I remember they did have a CD last year but haven't seen anything like that this time. The devices do have a couple of preloaded samples but definitely not 100 full books.
Since those books were just public domain books available everywhere, I suggest you to just download some
from here,
Feedbooks,
Manybooks or
PG. If your son likes SF, make sure to get some from
Baen Free Library or
Baen CDs.
Download either EPUB of LRF (BBeB) formats.