When my daughter was in high school, she and I would solve crypto quotes for extra credit.
Frequency analysis.
But it has been a long long time since I did that.
Thanks.
Frequency analysis (HAL helps) is a good starting point but patterns like THAT, PEOPLE, ALWAYS, etc. are useful. Taking a shot at the author, e.g., KPIX EFPSU (MARK TWAIN). Don’t forget the Concordian twins LMFSA VMFKW IGILOWT (’RALPH WALDO EMERSON’) and TWUCG ZQSYZ JTMCWQH (’HENRY DAVID THOREAU’). Both with the pattern 5-5-7, but different locations of repeated letters.
Enjoy!