Stanislaw Lem is mainly known as a science fiction writer, but he transcends this distinction in many ways. He was part of the wave of SF writers working in the 70s that brought us the first masterpieces of Ursula Le Guin, Samuel R. Delaney, and so many others who were using their fiction to comment on the failure of the 60s milieu to change the culture, especially since the 80s brought on the rise of a conservative class that was enmeshing America into a more materialistic stance. But it would be ironically in the 80s that SF was finding its sea legs as a respectable literary genre.
That said, Lem is a Polish writer, and inasmuch as he participated in the SF scene of the 70s, his scholarly work suggested he found in SF something other than its readers were expecting. Since he was highly critical of the American writers whom he didn't think were reaching truly literary strength, he suggested that the idiom of the genre was being more led by writers like Philip K. Dick, someone who was less interested in the science in fiction but the more transcendent properties inherent in manipulating reality. Lem's "Transfiguration" novel is actually not a SF novel, but war literature depicting the Nazi abuses in Poland around 1939 as seen through the eyes of a doctor superintending a clinic for the insane. It would be then a searching examination of the abuses of a minority culture not just in the Nazi's who kind of just show up on cue at the climax of the novel, but also in the various ways the doctors who are really ignorant of how to improve the conditions of the people they are supposed to be helping.
Once the doctor has decided to take his friend's advice, after the death of his father, and taken up a position in the psychiatric hospital, we can be struck by how mundane the descriptions of the residents are. Lem seems to rely on popular notions of what the insane might have looked like to outsiders as descriptions of them come to seem stereotypical. In fact, many of those residing in the hospital are simply there because they see it as a way to avoid homelessness. The doctor eventually befriends a man who is presented as a sage, and wholly sane except for his eccentric forays into esoteric philosophy. This is where the ideas of the novel reach full expression, as the doctor kind of intuits that the sagely properties of his inmate may just help himself reach a form of transcendence. This may be trading on the ancient ideal that the insane were "touched" by God, giving this population its first stigma as crazy but somehow having God's ear. Examining the reports of middle ages mystics may just lend credence to this view, as their visions seemed to contain signs of what we would call mental illness now. As to whether this constitutes an actual pathology or not remains to be argued, but this idea powers Lem's narrative. Once the Nazi's show up, of course we have to have the obligatory killing of the disabled which the Nazi's were known to do, but Lem is a truly literary writer, and shows s strength of style that makes him one of the great stylists to have ever worked in SF (albeit this is not exactly SF). But genre issues aside, great literature may sometimes skirt around the more vaunted ways we want to view it, but this novel bears reading for the true sense of mastery that pervades its pages. If you haven't been exposed to Stanislaw Lem before, you might not want to start with this novel, but make your way through his canon until you're ready for this example, which is essentially war literature. And if you haven't been exposed to war literature before, well, I wouldn't exactly suggest Sartre either, as impenetrable as he can be, but if you have a hankering for meaty ruminations which we often find in those who've rubbed shoulders with the Nazi's, maybe get a sense of the absurdity of it all by diving into Quentin Tarantino's "Inglorious Basterds," and then maybe make your way into Philip K. Dick's "The Man in the High Castle," an alternate history novel giving us the horrific possibility that Japan and Germany actually won the war. This book predates that 70s milieu, but Dick is a 60s writer, whatever decade we happen to find his books in, so if you're interested in SF as a reaction against powerful forces, Dick and Lem are great authors to get acquainted with.