Psychohistorical Crisis was great. Definitely a novel I need to re-read at some point.
The three books of the Second Trilogy all blur together for me at this point, but it was an ill-advised project. They should have just created their own universe to develop their ideas in; in terms of being respectful to the source material, it was disastrous.
I'd be happy to write
Foundation And Galaxia, though. Asimov felt he had written himself into a corner, but I know a very Asimovian way out of it.
