Hemispheres would outrank 2112, in my opinion, save that it's spoiled because the first part of the story, "Cygnus X-1, Book One: The Voyage", is on the album Permanent Waves instead.
OTOH, I'd nominate Moving Pictures as their best to date - haven't had a very good chance to listen thoroughly to Snakes & Arrows yet.
(Why, yes, I'm a bit of a fan - why do you ask?)
Trivia moment: In one issue of Justice League, Green Lantern John Stewart has drawn monitor duty, and the Flash (Wally West) is keeping him company. GL is reading a book of Neil Peart's published poetry. The Flash notes that Rush is sometimes called "math rock", for their habit of changing time signatures within a song. He also says they're his favorite band, because when you have a hyperaccelerated metabolism, plain old 3/4 or 4/4 time gets pretty boring after a while.
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Sodium is a metal that reacts explosively when exposed to water. Chlorine is a gas that'll kill you dead in moments. Together they make my fries taste good.