I'd recommend to any of our friends interested in relics the book "Relics" by Joan Carroll Cruz. Covers a whole of different types of relics.
Thanks for the book recommendation. I'm particularly interested in the incorrupt bodies of the saints. It's sad that current catechesis ignores all of the miracles associated with the Church. Sure, this is "gravy" for people formed in their faith, but these miracles offer a simple and direct "proof" of God's existence that is very accessible to children.