This is one of Zappa's true monsters, a great, ambitious album that is one of his masterworks.  It's arguably the most complex album he ever did, especially in musical terms.  Many of the themes on this album were revamped for orchestra years later (like on Zappa's last classical album, The Yellow Shark), which shows you the great complexity of this work.  This album was actually a soundtrack for a film that took years for Frank to complete, but more on that later.