Two very good books for the beginner tumber are; Modern Rock Tumbling by Steve Hart and How To Tumble Polish Rocks Into Gems, Secrets of the Pros Revealed by Edward E. Smith.
Also, if you are a tumbler I recommend you visit the Rock Tumbling Hobby (RTH) forum https://forum.rocktumblinghobby.com/. Browse the catagories they have and if you have any questions enter them into the search bar and press enter.