This novel was originally published, in the Polish language, in 1964 and then didn't appear in English until 1973. It thus predates the Moon landing by five years, and, IMHO, retains some of the trappings of the prevailing science fiction of the times. For example, very large spacecraft landing on the surfaces of planets, and devices with terms like "automat" and "electronic brain". Ray Bradbury had "rockets" landing on the planets of other suns, also, but his focus was on how space travel would change people(or not), etc. Lem's focus is far more scientific and his protagonists are typically professionals trying to understand particularly mysterious aliens. But he still manages to keep his descriptions of his tech general enough for it to still play well even here in the jaded 21st century.

The Invincible is an 80 kiloton "cruiser" in Lem's grand tradition of large, powerful and lavishly-equipped spaceships that, despite their office bldg dimensions, have the power and ability to actually land on the surface of one gee planets, rather than park in orbit and send out smaller craft. It is loaded with squads of various types of robots (indispensable helpers in Lem stories) and several heavy ground and air vehicles, along with adjustable force fields to protect both the main ship and the various expeditions it sends out. It can even launch satellites into geosynchronous orbit for surveillance, and possesses antimatter "annihilation weapons" that evaporate the atomic structure of targets, as a last resort. The crew is also a well-chosen and essential asset, with experts in all sciences mankind has found useful among the stars, and who go about their duties with efficiency and insight. The discussions between the 19 (out of 80) crewmembers that form the scientific administration of the ship are fascinating excursions into the best of hard science fiction. It is good to see trained professionals puzzling out an alien mystery and not just running scared from space monsters. Thus, Lem shows us mankind's best being confronted by a lethal unknown, and coming away with a deeper understanding. Indeed, Lem is trying here to gaze into a possible future for a robot lineage left abandoned by a race of beings fleeing the nova of their home star. This isn't a tale of robots like Klapaucius and Trurl of "The Cyberiad" (which he published a year after this novel) ; this is a hard science fiction look at what could really happen if robotic entities are left to their own form of evolution for hundreds of thousands of years after their own creators have long since died out.

Despite all this, the fate of The Condor, Invincible's sister ship that it was sent to find on Regis III, remains a mystery for nearly a month of careful and comprehensive investigation . Lem takes us along on the mystery and reasoning of the scientists, until the amazing truth arises to render nearly 50% of The Invincible's crew either blank-minded children, or dead.

Where other novelists might want to add intrigue among the crew or commanders, and action triggered by subterfuge or incompetence, Lem portrays a shipload of men who, though human in every way, are an idealized version of such. They stick to procedures and do their jobs in the background of the action, which frees the story to move forward as a progression of discoveries that reveal the nature of their foe. I sincerely hope that future expeditionary forces from Earth are just like these guys.

I read this book about 40 years ago in it's original language. It made an impression on me. Loved sci-fi ever since. One of the best Lems work. I would recommend finding an edition translated from Polish to English.

Stanislaw Lem tends to be unrivalled when it comes to philosophical insights into first contact with alien intelligence. Unfortunately, as philosophising for Lem often tends to spill over into over-philosophising, this usually comes at the expense of accessibility and readability. The Invincible is a rare and rather successful exception to this, which makes it an excellent introduction to Lem for novice readers. And even if the underlying theme is the same as in a number of Lem's other works – man's understanding with alien intelligence is doomed from the start – the take on it in the Invincible, combining elements from the mystery, horror and action genres and offering a curious environmental angle is both rather unique and makes for a real page turner.

The novel opens with the landing of a vast and powerful space ship, the Invincible, on Regis III. The Invincible is sent to investigate the loss of its sister ship, the Condor, on the desert planet. The discovery of the horrific disaster that has befallen the Condor and the first encounters with the mysterious force behind it gradually build a growing sense of terror among the crew, which turns into genuine bafflement and a feeling of powerlessness as the enemy is revealed and proves undefeated despite all of the crew's efforts.

As the only realistic prospect of subduing the peculiar intelligence developed on Regis III is to cause planet-wide destruction with nuclear bombs, the crew come to the realisation that – just like the ocean or the wind or a swarm of bees – this intelligence has become an integral part of the planet's ecosystem. Seeking revenge on it for Condor's destruction would make just as much sense as nuking an ocean for wrecking a sailboat. The ending is anti-climatic. Humans have no place on Regis III. Both man and the Invincible – now quite defeated – need to go home.

Like many of Lem’s other books, this one was not translated into English directly from Polish. A German translation was used as an intermediate step, but at least Lem authorized the translation as he was fluent in German. Still, some meaning has been lost.

‘The Invincible’, written in 1964, was his third book dealing with an alien intelligence that was incomprehensible by humans (after ‘Eden’ and ‘Solaris’). It describes a visit to a desolate planet where the previous ship lost contact with Earth a few years ago. The humans arrive quite cocky, equipped with heavy equipment and weaponry, only to find a hidden alien force that seems impossible to defeat. 'SF thriller' would best describe the genre, but it also carries a strong message about human inability to understand another form of intelligence.

A must read for every SF fan.