Check out "Ecofarm" by Charles Walters. It is one of the best books on soil chemistry I have ever come across. Clay has wonderful properties if amended in a balanced manner.  

You can use Logan Labs for soil testing. This company KISS organics has an easy way to get a soil test done and provide you with recomendations based on the soil chemistry. https://www.kisorganics.com/products/soil-test-analysis-report