It's origins in a set of linked short stories are clear. It has interesting ideas. It suffers a lot from being essentially a set of cardboard cut-outs talking. The grand sweep of history is entertaining, and the science of psychohistory is delightful nonsense.
Asimov as a prose stylist is only OK.
In the end, I am not sure that it deserves the classic status that it has, but it is not a bad book.