I love Asimov's Foundation series and am on my third time of reading it - and I almost never re-read a book. He is a master at designing a thought-provoking fast-paced novel and makes you want to travel along and explore the universe.
Written in the late 1970s early 1980s this classic series is well worth reading. It has much in it that we are beginning to recognize as 'now' rather than 'future.'
#4 in Foundation series. They are all good!