King Crimson's music was made during five distinct eras, and has had approximately seven hundred different members. When listening, start with one album from each era:

• First era late 60s early 70s/ early progressive rock: Court of the Crimson King, In The Wake of Poseidon, Lizard, Islands. Start with Court.
• Second era mid 70s/heavy progressive rock and sorta metal: Larks' Tongues in Aspic, Starless and Bible Black. Start with Red.
• Third era 80s new wavey sort of: Discipline, Beat, Three of a Perfect Pair. Start with Discipline.
• Fourth era 90s I don't know what to call the genre: Thrak.
• Fifth era 2000s metalish sort of: ConstruKction
  
  of Light, Happy With What You Have to be Happy With, The Power to Believe. Start with Power to Believe.