Octopus is one of the best albums by Gentle Giant. IMHO, they were one of the most under-rated bands from the mid seventies progressive rock era. Although they weren't a "guitar solo" oriented band, they did have great guitar work on their albums. The best guitar solo on Octopus (for solo freaks!) is the solo on River.
I saw Gentle Giant a number of times. They played the Whiskey a Go Go for four nights, two shows a night, and I saw all eight shows! They were amazing to watch in the small club environment.
Other great albums by Gentle Giant include In a Glass House, Three Friends, and The Power and the Glory.