Asimov published the original Foundation Trilogy in the '50s, but then added a few more novels in the '80s. He also used this as an opportunity to incorporate his other novels and series into this same universe (kind of like almost all of Stephen King's novels now relate to The Dark Tower series). I'd enjoyed the original trilogy and would have been fine if it had simply been left where it was, but this novel definitely kept me interested.
One of the politicians from Terminus suspects the Second Foundation was not actually destroyed at the end of the last novel, and that they continue to manipulate events to make sure the Seldon Plan comes to frutition. Of course, Trevize hates this idea because in his mind it takes away the idea of free will. As a result of some political scheming, he ends up attached to an old historian in search of Earth. Pelorat, the historian, has an interest in Earth unlike pretty much everyone else in the universe which is based on both historical and biological evidence. All the planets have clearly been settled by one originating source since the same life forms exist throughout. Most of the planets had little natural life to begin with, and much if it barely remains now. Trevize uses the search for Earth as a cover to discover the Second Foundation, and also decides that it is very likely the location of the Second Foundation (which is of course wrong).
Meanwhile, Gendibal, a promising young speaker of the Second Foundation has seen a flaw in the plan - the lack of flaw. This gives him the idea that someone else besides the Second Foundation is manipulating events for an unknown purpose. He believes that Trevize is somehow the key to all of this.
As I said, I enjoyed the novel, mainly because I liked the idea of the search for Earth - I'm also a Battlestart Galactica fan. I always enjoy seeing how authors think that Earth/current society might be viewed or forgotten by future generations, and how certain actions might be analyzed. As a result, I was intrigued and liked Pelorat's parts where he explains his research quite a bit. Trevize was cocky but for the most part, I liked the character. I didn't really warm up to Gendibal much - he was just too full of himself and his search wasn't quite as interesting to me.
While Asimov had already started including stronger female characters in the last two novels of his original trilogy, the years between the novels definitely are noticeable in relation to gender portrayals. The current Mayor of Terminus, and therefore the most powerful person in the universe, is a woman, Mayor Branno. Additionally, she is very intelligent and able to manipulate events. I liked her better in the first half, though, since in the second half, she seemed too imperialistic. Gendibal takes a Hamish woman (the planet the Second Foundation inhabits is a farming world, and she is one of the locals that serve as a cover) on his trip with him to use her mind as an alert system (due to complicated mind reading things). At first it rather annoyed me how much he condescended to her which was due to her status as a nonmentalist. He obviously thinks that as part of the farming community she is not as intelligent or developed as he. Actually this whole part kind of reminded me of Octavia Butler's Patternmaster. However, she plays a much more important role later, and also shows how easy it was to dupe Gendibal due to her gender and social class (much like in Second Foundation, a woman acts like a complete idiot and ditz as a cover). Trevize, while likable, is also portrayed as a complete womanizer. At one point he meets a 23 year old woman and keeps referring to her as an untrained girl - which was annoying considering that she was 23, and given his leadership, he should know better than to think of women as girls. The last part of the novel is a little bothersome, though, since the young woman keeps getting ogled by 50+ year old men, and makes comments about how she dressed liked that for their pleasure and has a body people have died for. However, Asimov explains the greater motivation behind her desire to please. Still could have done without some of it, but at least it makes a kind of logical sense within the novels. While Asimov has included more women in this one, his male characters still have a tendency to underestimate them. It's also interesting that Trevize and Gendibal both have very strong female antagonists/politicians to contend with in their own worlds that are part of the reason they end up on these missions. In a way, the female characters fall into certain stereotypical categories: the sexless shrew, the sex kitten and the innocent, pure Madonna like figure. Asimov uses these stereotypes and adds deeper layers to the personas. While the novels are definitely still male-centric, it was nice to see that at least women are appearing in them and playing a role.