Fushi no Kami ~Henkyou kara Hajimeru Bunmei Saiseiki~

From J-Novel Club:
When the civilizations of yesteryear fade from memory and become fanciful fantasy the only evidence of their existence are books. Ash, a young boy living in a remote farming village, holds a secret he possesses memories of a distant and more bountiful past life. Days of toiling in the fields have given rise to a burning desire: to bring more enjoyment to the everyday doldrum of his dreary present day. And while books may be the answer, Ash can’t actually read. But where there is a will, there is a way. Join Ash as he battles illiteracy and sets his sights on a better life!