Have any books has been written about Ripple and Litecoin? I buy some ebooks about cryptocurrency, bitcoin and blockchain from 
http://sacredtraders.com/index.php/product-category/crypto-book

Have there been any books written about Ripple and Litecoin?
I found a few books on Amazon that may interest you.

Ripple Book

Generic book explaining Ripple

Litecoin


These books can be very generic.
For understanding the technology, I would recommend that you read the white-paper (yellow-paper if super interested).

Whitepaper-Ripple

Solutions using Ripple

Ripple whitepaper explained


Video Resources

Ripple consensus algorithm explained

Litecoin explained by its founder


P.S. As of writing this answer, there's no official whitepaper for Litecoin, as it is a fork of Bitcoin and uses similar underlying technology with the claims of being faster than its predecessor.