Amazing raw, energetic live talent and a lot to offer as far as auditory fullness and clarity. They are a treat for the ears, that's for sure. The Mars Volta - I dare say - stretch musical and lyrical boundaries in this millenium like The Doors, Floyd, Zeppelin, and Hendrix did back in the day. Their musical and lyrical talent, combined with their stage energy, put them right on par with the aforementioned giants of rock. They are underrated legends, IMHO.
Check it: The Mars Volta - Cicatriz ESP, Part 1 (about seven minutes)
Cicatriz ESP, Part 2 (a little bit over seven minutes)
The Mars Volta's 2003 album "Deloused in The Comatorium," is based on a short story written by the lead singer about a friend of his who overdosed on morphine. The link is to a PDF file. Fascinating shit!