"YES CANNOT BE YES WITHOUT JON ANDERSON!"
No. If you think that, you can just leave.
Jon Anderson, the main vocalist (and percussionist), left the band antecedent to the release of YES' 1978 release Tormato. This left many, MANY people stunned at this, and it was a collective idea that YES was finished. "After all," people said, "no one could replace the great vocalist who had been the soul head of the band during his age."
So after Anderson resigned, the producer of many previous YES albums, Trevor Horn, took his place as lead vocalist. The band, being under ever increasing stress to make a YES album for the ages even with the lack of Anderson.
And In my opinion, they did it. Although perhaps not as "progressive" as say Fragile or Close to the Edge, Horn took YES in a brief direction of progressive hard rock.
The album, starting out with the ten and a half minute epic 'Machine Messiah', comes in with very traditional - heavy metal edge. This song has been voted on boards across the internet as the heaviest YES song there is. The metal shouldn't scare you away from the aspect of the epic not being good old progressive rock. Having a ten minute recording, there has to be fluctuation from sound to sound in order to not bore the listener., and they do it very well. You'd have to listen to the track itself to know what I'm talking about. But TL;DR, this song is my favorite from the album. The album bridges with the slightly unnecessary 'White Car' into 'Into the Lens'. The latter is extremely reminiscent of RUSH's older material, and I think it would be enjoyed by anyone who likes them.
The album does retain, as I said before, fluctuations between prog rock and harder, RUSH-y rock. The prog is, however, undoubtedly YES. The tracks (although they are few), will keep you pretty interested throughout. It is true that Horn may not be able to hit some of the high notes that Anderson could, but to me, this is kind of a relief. High-pitched vocalists have always been a pet peeve of mine.
From a jazz point of view, you will not find much on here. This is less the old jazz-fusion-Anderson era and more, as said before, a progressive hard rock album. I would pick it up though for an interesting listen.
But overall, pick up the album. It is interesting, and important to any fans' YES collection.
Go give it a listen.