Here is a list of The Foundation Books Ranked, According to Goodreads.
Second Foundation 4.27
From the blurb:
The First Foundation has been defeated, crushed by the formidable mental powers of the Mule. But whispers of the mysterious Second Foundation, the only hope of defeating the Mule, are beginning to spread…
Foundation and Empire 4.22
From the blurb:
Led by its founding father, the psychohistorian Hari Seldon, and utilizing science and technology, the Foundation survived the greed and barbarism of its neighboring warrior-planets. Now cleverness and courage may not be enough.…
Foundation 4.17
From the blurb:
For twelve thousand years the Galactic Empire has ruled supreme. Now it is dying. But only Hari Seldon, creator of the revolutionary science of psychohistory, can see into the future—to a dark age of ignorance, barbarism, and warfare that will last thirty thousand years.…
Foundation’s Edge 4.17
From the blurb:
After a long war which saw the First Foundation emerge victorious, the Second Foundation is now believed to be extinct, and all records of planet Earth’s existence have been erased.
No one suspects that the Second Foundation could still exist. None, except Council member Golan Trevize, who finds himself ordered to leave Terminus, accompanied by historian Janov Pelorat, in order to find it.…
Forward the Foundation 4.16
From the blurb:
As Hari Seldon struggles to perfect his revolutionary theory of psychohistory and ensure a place for humanity among the stars, the great Galactic Empire totters on the brink of apocalyptic collapse. Caught in the maelstrom are Seldon and all he holds dear, pawns in the struggle for dominance. Whoever can control Seldon will control psychohistory—and with it the future of the Galaxy.…
Prelude to Foundation 4.15
From the blurb:
It is the year 12,020 G.E. and Emperor Cleon I sits uneasily on the Imperial throne of Trantor. Here in the great multidomed capital of the Galactic Empire, forty billion people have created a civilization of unimaginable technological and cultural complexity. Yet Cleon knows there are those who would see him fall—those whom he would destroy if only he could read the future.…
Foundation and Earth 4.07
From the blurb:
Golan Trevize, former Councilman of the First Foundation, has chosen the future, and it is Gaia. A superorganism, Gaia is a holistic planet with a common consciousness so intensely united that every dewdrop, every pebble, every being, can speak for all—and feel for all. It is a realm in which privacy is not only undesirable, it is incomprehensible.…