“Sphere” is a psychological novel which revolves around an alien object, a sphere, found on a spaceship discovered on the bottom of the sea. While no actual alien is present in the book, the subject of the potential appearance of extraterrestrial beings, their behavior and means of communication, are thoroughly discussed. The mysterious sphere, which seems to have psychic abilities, is considered by some of the characters as a test for humanity, but others believe that the evolutionary gap between races is so large that the aliens probably did not even consider the humanity as a noteworthy element in their plans.

This story follows a group of alien space explorers who investigate the human race and are baffled to find out that their research subjects are made out of meat. To the plasma-based creatures, the idea of walking sacks of meat capable of thought is simply ridiculous. The aliens finally decide to leave the humans alone and pretend they simply did not see them.

The famous trilogy of humorous books documents the travels of Arthur Dent, a normal human being who gets lost in the comical infinity of the Universe. While most of the alien races present in the books are humanoid, there are a few very interesting interpretations of how an alien could look. The Hooloovoo, for instance, is a super intelligent shade of blue which exists between two dimensions and can be manipulated by light refraction. The babel fish is also a very original creature; it eats unconscious brainwaves and excretes them as comprehensive thoughts. When placed in the ear, they act similar to a universal translator.

In “The Shadow Out Of Time” , Lovecraft describes the Yith, an alien race that is able to transfer themselves mentally from one body to another, preserving their race for eternity. The bodies of the Yith, though not their original form, are extremely interesting. They are cone-shaped creatures with eyes encircling their heads and a multitude of tentacles helping them manipulate objects. Since they can always project themselves in time and space, their race is never truly threatened with extinction.

The centerpiece of Stanislaw’s novel is how the difference between humans and extraterrestrial life forms will make any meaningful exchange practically impossible. Space explorers discover a planet that is completely covered by a single conscious creature resembling a planet-wide ocean. While the scientists monitor the creature, the alien probes their mind in order to better understand human beings. In the process, repressed memories are being brought to the surface and the main characters realize that the human mind is far more complex than previously thought

Wells details the lunar expedition of an eccentric scientist and his companion. After reaching the Moon, they are surprised to find out that the Earth’s satellite is far from being barren. The hollow interior of the Moon is in fact populated by the Selenites, a highly organized insects-like race of aliens. Within the selenite society, there are several sub-species which have evolved depending on their main function. Some have incredible memories, others have adapted to being farmers or tool users and some have even fashioned themselves into musical instruments.

The aliens described in Clarke’s novel are similar to Earth’s aquatic fauna. Some are enormous, heavy creatures that resemble whales while others are smaller and resemble sharks. All of these creatures live in the clouds of Jupiter.

Asimov describes a parallel Universe where our laws of physics do not apply. This Universe is populated by a very strange race which has three genders. The member of each gender differs from their counterparts so radically that one could believe that they are of different races. These aliens are nurtured and taught by greater beings that live underground. When the three genders mate, they reach the final stage of their evolution and become one of the greater beings.

The Cheela are described as being just as intelligent as human beings, but much denser due to the gravitational field of their home world. The most amazing aspect of the Cheela is that their atoms are not bound together as ours are, making it possible for them to transfer neurons between themselves. They live on the surface of a neutron star and develop amazingly fast.

In “Star Maker” you can find a multitude of incredibly beautiful and imaginative descriptions of alien life forms, including a group of bird-like aliens who develop a common mind, a race of creatures resembling ships who form a hierarchic society and a race of fish and arachnoids who develop a very close symbiotic relationship allowing them to eventually travel through space.