tek's rating: 
(I intended to give each book its own rating, in addition to this rating for the series overall. But then I changed my mind, and I'm just doing an overall rating. I may change my mind again, later, though. Each book I would individually rate perhaps slightly lower than the overall rating, however.)
Foundation (series), by Isaac Asimov (originally & predominantly)
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Caution: the various reviews here may each contain potential spoilers, so be warned... but for the most part, I'll refrain from giving away any truly important details (I'll save spoilers about each book until my review of the next book in the series), though this might end up being almost more annoying than major spoilers would have been...
I first read at least the first three books in the series when I was in high school, I believe. And I loved them, but I never finished the series. Which is rather complicated, actually. The first book is comprised of four different stories originally written in the early 1940s, along with an introductory story written in 1950, I guess, specifically for the republication of the stories in book form in 1951. The second book was comprised of two more stories written in the latter half of the 1940s, published in book form in 1952. And the third book, published in 1953, was comprised of two more earlier published stories. So, these books which were basically just collections of stories, now comprised the Foundation Trilogy. Which didn't complete the story, actually, but Asimov wasn't really planning on writing any more of this particular story. It wasn't until 1981 that his publisher forced him to write a fourth entry in the Foundation series, and this, for the first time, was actually written as a single novel from the outset (even if it started with 14 pages Asimov had begun writing 8 years earlier and abandoned). Throughout the 1980s, he wrote a few more Foundation books, the last two of which were prequels. So the story still wasn't finished. (I intend, btw, to read and review the novels in the order they were written, rather than in the order of the stories' chronological setting. You, of course, are free to read the books in whatever order you wish.)
Other authors have, since Asimov's death, written authorized books set within the Foundation series (also prequels), and as far as I know, the story has never truly been concluded, since it was meant to span 1000 years, but only spans about 500. I also need to mention that the Foundation series is ostensibly set within the same fictional universe as other of Asimov's science fiction books and stories. There's the Robot series, which may be thought to include almost any book or story about robots (whether by Asimov himself or others writing within his universe), and these are mostly set about 20,000 years earlier than the Foundation series. I mostly think of this series as including four books, though. I know I read three of them, and possibly the fourth (though I don't remember for sure). I don't remember any of these books well, and hope to reread them eventually and write reviews. The fourth of these is set around the same time as the Empire novels, of which I believe I've read one. This is set much later than most of the Robot novels, and basically consists of just three books. The Galactic Empire lasted for 12,000 years, until the fall, the aftermath of which is the subject of the Foundation series. Which, as I said, is supposed to span 1000 years.
And I guess that's about all I can think to say, by way of preamble to my actual reviews. (Oh, other than that the series, in 1966, won a Hugo award for all-time best series, beating out Lord of the Rings; I expect other series were nominated, but those are the only two I know of. I tend to wonder if it'd work out that way if a vote was held today, but I think it very well might, considering the vote isn't by general public. In any event, obviously, the award was for the first three books in the series, as the others hadn't yet been conceived, let alone written. Not too shabby, for a series that had no ending, and probably will never be more than halfway done.) Now, I intend to reread the Foundation books I'd read before, and write reviews of them here, as well as reading books I hadn't previously read. (As I re-read the first three books, I was struck by how fresh the plots seemed to me, how little I actually remembered of them.) ...Then I'd like to move on to reading and reviewing Robot novels and Empire novels. All great stuff, of course.
I should also mention that throughout the books (excepting the fourth and fifth), we sometimes see quotations from the Encyclopedia Galactica, 116th Edition, published in the year 1020 of the Foundational Era, so it can be assumed from this that the Plan (explained in the first review) eventually succeeds, even if we never get to see exactly how it all plays out, in the end. Though other than spoiling us of this ultimate fact, I don't usually feel that these entries add much, usually, to the story. But whatever, they don't hurt... with the possible exception of making you wish you could read more of the Encyclopedia than just these incomplete excerpts on each subject. And while we're on the subject, I should also say that the term "Encyclopedia Galactica" has been referenced in any number of other fictional universes, perhaps most famously in Douglas Adams's "Hitchhiker's Guide to the Galaxy" (which I desperately need to review someday.) But this series is where the term originated.
Anyway, you may read my reviews of each individual book in the Foundation series by clicking the buttons at the top of this page.