Fushi no Kami: Henkyou kara Hajimeru Bunmei Saiseiki

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!

(Source: J-Novel Club)