The Invincible is an elegant, tragically beautiful story filled with technology and strangeness - all things a reader might expect from a novel by Pould Anderson or Andre Norton at their best.  But when the story reaches its logical development, when we have learned everything we can about what has been happening to the starship Invicible's crew, and what has happened to the previous expedition to Regis III, a planet where evolution has taken a mechanical-cybernetic direction, then Lem continues to climb, making painfully real to the reader the sight of humankind and its values confronted with an alien, mechanical system.

George Zebrowski, The Magazie of Fantasy and Science Fiction