Unfortunately, Lem’s most thought provoking book, Summa Technologiae (1964), was never (completely) translated into English.
There is only a partial translation into English: http://web.archive.org/web/20041012053805/http://wwwnlds.physik.tu-berlin.de/~prengel/Lem/contents.htm
Russian translation: http://lib.ru/LEM/summa/summtitl.htm
Unfortunately, Lem’s most thought provoking book, Summa Technologiae (1964), was never (completely) translated into English.
There is only a partial translation into English: http://web.archive.org/web/20041012053805/http://wwwnlds.physik.tu-berlin.de/~prengel/Lem/contents.htm
Russian translation: http://lib.ru/LEM/summa/summtitl.htm