Meaning of RUSH song's?

hey i love rush they are my most favorite band ever but some of there songs i cant understand the meaning of the song i get 2112 and Cygnus X-1and Xanadu and the TREE'S. but one of the only shows i cant figure the meaning out is the Hemispheres song i no that it has to do with the greek gods fighting and its the second part of Cygnus X-1. but other than that i cant figure out what the songs purpose is so if you can help me.