Kindle book to learn how to play guitar or piano free at Amazon

My five-year old son has been bit by the bug for The Voice and has been begging for singing and guitar or piano lessons. I'm not too sure it will be more than a fascination for him since he's shifted between every talent you could think of within the last year. It's great that I found free Kindle books on Amazon on learning how to play the guitar, piano and sing. I've already found a few friends who are willing to loan old guitars and electronic keyboards that their children have grown out of so this is a cheap alternative to him getting lessons from a professional. It would give him a sense of how much hard work it will be and I'll probably see in a few weeks if this is something that he would like to do for the long-term.