"Apparently Lem's other works - Cyberiad at the very least - received more attention, and therefore did not flatly lump around in English, describing a great deal in monotone grey."

a. This is a very badly written sentence.
b. I am sorry about that.
c. It means:
c.i. Lem's other works have been translated into English.
c.ii. The book I have heard the most about re: its English translation is Cyberiad
c.iii. These books, but Cyberiad that I have specifically heard of, have received attention for being better translated than Solaris.
c.iv. This means that these other, non-Solaris translations had prose that did not "flatly lump around in English, describing a great deal in monotone grey".
d. In conclusion, the English translation of Solaris is an exception to the usual run of Lem-to-English translations, in that it is not a good one.