On a technical level the book allows itself only two impossible scientific leaps - the faster than light Alderson drive and the Langston Field shield system. Even those are treated in a convincingly realistic manner which takes nothing away from the believability of the book's technology. Beyond those two everything else is based directly on known physics. The mechanics of interplanetary travel are flawless, with ships accelerating or rotating to provide artificial gravity and fighting one another using nuclear missiles and powerful laser cannon.
Against this background, the authors have created a story which is mysterious and involving.
A sequel to The Mote in God's Eye, titled The Gripping Hand, was written by the same authors over twenty years later.
Warning: Spoilers follow
Set around the year 3000 AD, in the book Humankind is slowly recovering from an interstellar civil war which destroyed the old Empire of Man. A new Empire has risen and is occupied in establishing control over the remnants of its predecessor, by force if needed.
An Imperial battlecruiser, MacArthur, happens to be on hand when an alien space craft arrives. Human ships use the Alderson Drive, which allows them to "jump" instantaneously between specific points in star systems. The alien craft, however, is a solar sail vessel which has taken many decades to cross between stars at sublight speed. MacArthur intercepts the craft and is fired upon by what turns out to be an automated meteor defence, but manages to capture it relatively intact. However, on arrival back at base the pilot turns out to be dead.
MacArthur and the battleship Lenin are sent to the Mote - the star from which the alien ship came. The Mote is so called because it is a companion star to a red giant, the two set against a great dark dust cloud - from a nearby Imperial system the cloud looks like a hooded man, with the pair of stars as an eye with amote in it. MacArthur carries civilian research teams intended to meet with and investigate the Moties, whilst Lenin is there to "ride shotgun" on the mission, avoiding all contact with the aliens. The Mote has only one Alderson point leading to it, and to reach this the ships must actually penetrate the red giant itself before using their drive systems, only possible because they have the Langstron field shield technology.
MacArthur makes contact successfully with the Moties, who are separated into various castes which are physically somewhat different from each other - mediators who conduct diplomatic negotiations, browns who perform engineering tasks, masters who make the decisions, etc. The Moties have much advanced technology and seem friendly and willing to share. Indeed they would likely have been formidable competitors to Humanity, except for the fact that they lack Langston Field technology and so are unable to leave their system via the Alderson point leading into the red giant.
As MacArthur prepares to leave, however, disaster strikes. A pair of Motie animals called Watchmakers have escaped on the ship, and although they were thought to have died they have actually been breeding furiously. Watchmakers are not sentient, but have an extremely highly developed instinct for technology - and unknownst to the Human crew, have been quietly redesigning and rebuilding MacArthur. The crew is forced to abandon ship, which Lenin then destroys. Lenin proceeds back home, taking with it Motie ambassadors - in violation of her orders to avoid contact with the aliens, which her captain does only after great debate.
As Lenin leaves, several MacArthur crewmen who managed to escape the ship in lifeboats land on the Motie planet, Mote Prime. Exploring unsupervised for the first time, they make a startling discovery - the Moties are not nearly so peaceful as they seem. Their biology forces the species to be extremely prolific, with a birth rate that ensures a neverending population explosion. Once the population pressure rises high enough, massive wars result which kill off almost everybody - only for the survivors to rebuild and repeat the cycle again. The Moties are utterly convinced that these cycles cannot be ended by any means. MacArthur's crewmen also find that there is a Motie Warrior caste, far superior in combat to any Human soldier, and these ultimately overwhelm and kill the Humans despite some help from a friendly Motie Master.
Back home, the Empire holds talks aimed at establishing trade and peaceful relations with the Moties, not realising what a disaster it would be to allow the species loose on the galaxy. Fortunately, the Humans at the conference manage to put together various clues they have picked up during the course of the story and work the problem out in time. It seems that they will have no choice but to send a fleet to destroy the Motie civilisation totally, but at the last minute the Motie ambassadors convince the Humans to instead blockade the Alderson point and keep their people confined to their own system for at least the forseeable future. The book ends with one of the Motie mediators predicting that the Humans will take over the Motie civilisation after the next collapse and wondering if perhaps the Humans might be able to force an end to the cycles after all.