Progressive rock is, or was, by definition pushing the boundaries of what could be done with music, and VdGG were one of the pushiest. With this album, they probably reached their peak - the albums previous to this were stepping stones toowards this complete album; the later albums are less radical musical statements.
All three tracks on this album are introspective pieces about aspects of the human condition, and I cannot think of any singer/song-writer who looks deeper into the depths of a human soul than Hammill.
Many people, including Hammill himself, seem to consider Lemmings as the least good track here, even a disappointment; for me it is a very powerful song, at first attacking the warlike nature of humans with venom, then finally mellowing into a plea to save ourselves from ourselves.
Man-erg takes the introspection to an individual level, and is a simple theme. We are all human, no more, no less, and it is this simplicity that makes the song so appealing. Yet again, as with Lemmings, the song ends on a somewhat optimistic note, that of acceptance of our condition. Or is that a pessimistic note?
And so to A Plague of Lighthouse Keepers: what can be said? Is this a tale of madness? A tale of us all? Is it even a tale about a lighthouse keeper? Maybe all of these. Whichever, it is an entrancing piece that is the essence of the album, and, consequently, the essence of Van der Graaf Generator. Whilst seeming to take us through the innermost thoughts of a terminal depressive, paradoxically it can be heard as an uplifting and moving song. However it is received by the listener, it is the central track of any VdGG collection.
So to answer the initial question: is this the best progressive rock album ever? Well, for me, there is no question about the answer - absolutely yes.