R&A and USGA Rules Publications
The R&A and USGA ‘Official Guide to the Rules of Golf 2019‘ is now available in a Flexi-bound hard-copy from Amazon.co.uk
Contains everything you need to know, including ‘Interpretations’, (which was the old ‘Decisions’) and ‘Committee Procedures’
Click here to go to the Amazon webpage
If you do not wish to possess a Hard-copy then the Mobile Apps for iOS or Android devices are excellent, and can be downloaded from here.