Being relatively new to the Galaxies Greatest Comic myself I get excited seeing others discovering Dredd, I'm glad you enjoyed it!
I started reading the Case Files just over a year ago and have since purchased the first 20 volumes. They are just that good and addictive, when you finish reading one volume you will immediately need the next!
After reading 19 volumes the Cursed Earth still stands as one of my favorite stories. If you are craving more you can also consider reading the Cursed Earth Uncensored which included colour spreads and additional progs not included in Case Files v.2 (vark did a great review on his blog well worth reading found here: http://myabsolutecollection.blogspot.ca/2016/08/judge-dredd-cursed-earth-uncensored.html
Vol 3. has the Dark Judges and Judge Anderson (and Bolland art), I recommend picking it up right away. Most people comment that Dredd really hits its peak starting with vol. 5 which is the Apocalipse War. Keep collecting and reading the Case Files, you wont regret it!