Foundation and Earth by Isaac Asimov (Published in 1986)

Foundation and Earth did not satisfy avid readers of Asimov (and fans of the Foundation series). After all, it was still only covering a period midway during the 1000 year period that was required to establish the second Galactic Empire, and neither covered the period after that, nor did it cover the period required for the establishment of Galaxia. Asimov's widow Janet revealed after his death that Asimov was unexpectedly somewhat of a loss after Foundation and Earth to write about what happened post that period. He ran out of ideas, and hence went back to detail the Foundation periods in more detail, with Prelude to Foundation, and Forward the Foundation. Further, Foundation and Earth did not have a very gripping continuous story line, almost with individual stories tending to a final end (that was supposed to establish the robotic theme that combined the Robot Series, the Foundation Series, and the Empire Series).



Foundation and Earth covers the time period immediately after the decision by Trevize in Foundation's Edge to use the basis of Gaia for building up a true Galaxia. However, he continues to have doubts, and is not sure whether he has made the right decision. He decides to continue searching for Earth, sure that the fact that Earth has tried to remove all traces of itself means that once he found Earth, there must be something there that would help him confirm his decision. So he sets out on an expedition along with Golan Trevize and and Bliss (a representative of Gaia) and travel to a number of planets, trying to get traces of the location of Earth.
They reach Comporellon, where they are imprisoned since the local inhabitants want to get control of the advanced gravity ship. In this case, Trevize literally manages to sleep his way out of this problem, and manage to get out of the planet. From Comporellon, they get the location of Spacer worlds (the first time Spacer worlds are mentioned in the Foundation series).
Next they reach Aurora, the most powerful Spacer world in its time, now a planet without humans and Spacers. They have an adventure here when wild dogs almost manage to pin Trevize down and only Bliss manages to save Trevize by using the power of Gaia.
They next land in Solaria, a world which was the most isolated of the Spacer worlds; with the inhabitants of that time even then refusing to meet each in person, instead meeting only through videographic depiction. The inhabitants have developed a great power called transducer lobes which allows them to channelize natural energy into great use, and live in big estates alone (and are now hermaphrodites, capable of handling reproduction alone). The 3 travelers land in the estate of one of them called Bander, who explains their history and eventually wants to kill them. They only manage to escape when Bliss reluctantly kills Bander (she blocks his energy use and that fries his brain since energy is still coming in but is blocked from going out). They also encounter the young child of Bander, Fallom, who will be killed since she is immature and cannot handle the estate. They manage to escape the robots sent to investigate the death of Bander and take Fallom with them.
They still have a Spacer world to go to, and reach Melpomenia, where they need to wear suits since the atmosphere has long vanished. They find a building with the coordinates of all the spacer world, and also encounter a moss that seems to grow on their suits and manage to kill it by using their blasters and then escape the planet without carrying the moss with them. These coordinates give them a way to find the likely location of Earth since they are able to possibly find the position of Earth at the center of these coordinates.
They next go to a Binary sun system from the above process, and reach a watery planet revolving around a star called Alpha Centauri. The inhabitants are friendly, but they soon discover (through a lady who has had sex with Trevize) that they are being poisoned. They also learn that there was an attempt to restore Earth's soil (as mentioned in Pebble in the Sky), but it was abandoned. There was also an attempt to terraform the planet of Alpha, but that was also left half way. They also escape from Alpha, but are pretty sure that they are close to Earth now.
And finally they reach the Solar System of Earth, first seeing huge gas giants including one that has large rings around it (just like the legend), and the third planet has a very large satellite. They have found Earth, but Earth is radioactive and does not support any life. They find themselves getting pulled to the Moon, where they eventually find R Daneel Olivaw, who explains that he called them here. He explains the whole history of how he has been guiding the human race for 20,000 years now, including the settling of Alpha Centauri, the creation of psychohistory, the setting up of Gaia. But he is out of time, his brain does not last long and creating a new one does not help. He wants to combine with Fallom, with her long life as a Spacer, it is enough to ensure that Galaxia is setup; Galaxia is the only way to safeguard the Galaxy against aliens from other Galaxies.