This page has links to a collection of online "books" about prospecting and metal detecting subjects of interest. Most of these were actual printed books or brochures that are now available as html or pdf documents. In the case of pdf documents especially you can download and save these creating your own library of essential information. Many of these are out of print and hard to find so we are very lucky they are being scanned and made available on the internet. Be sure to also visit Steve's Gu