The illiterate used to be catechized through sermons and visual aids, and we have a lot of those on radio, TV and the Internet so at least, there are options.
However, this is also an era of great literacy: books abound and the Bible, copies of which were immeasurably precious due to their effort and scarcity, is available in a gazillion copies in print, orderable from a whole lot of storefront and online sites at very inexpensive prices.
We are in a majestically blessed time in history, and I would just call to mind the old adage of our Lord: to whom much is given, much is required.
I would therefore not consider it prudent to turn away from books. They are still the best resource out there.