Same. They're one of those bands I see mentioned all the time on forums, yet I don't think I've ever once heard their songs on the radio, and I mostly listen to classic rock and oldies.
Ultimately, King Crimson are an album band, but this is complicated by the fact that most of their albums contain at least one or two pieces of pointless improvisational noodlings. Also, there's a great stylistic variety to their work, so depending on your tastes you can really start off the wrong foot with them.
First album is pretty much hour zero of British progressive rock. Strong jazz influences and lots of gorgeous mellotron. 21st Century Schizoid Man, Epitaph and The Court of the Crimson King are the highlight of that era. Keep away from the airy-fairy medieval hippie shit of the subsequent albums though.
Then there's the "heavy prog" phase of the early 1970s, which is characterized by a heavier rock sound. Larks' Tongues in Aspic is a great album from beginning to end, but it doesn't quite reach the peaks of Red (Starless, One More Red Nightmare, Red). While the best bits on Red are arguably "Peak Crimson", the album is marred a bit by the pointless noodling that is Providence.
And then there's the early 1980s / New Wave phase of King Crimson, which sounds like Talking Heads performed by a bunch of mathematicians. The singer of that era, Adrian Belew, does a pretty blatant (but good) approximation of David Byrne as well. It's a kind of fidgety post-punk sound with interlocking guitars and polyrhythms. Discipline is the best album of that bunch.