epic sci-fi

Robot - Isaac Asimov

Isaac Asimov's Robot Series ties in heavily with his Foundation series as a prequel series to it.
I would recommend reading the Robot seriers after the Foundation series.

Isaac Asimov's Robot series, are basically 4 Sci-fi detective stories set in the pre-history of the Foundation Universe. But they're not just "whodunnit" stories, they are full of the same political intrigue, adventure, trickery and suprtising plot changes, as are present in the Foundation series. And they tie in wonderfully, explaining how the Foundation Universe came to be.
One of the main characters in the series is R. Daneel Olivaw, who is also a character in the Foundation Series. The series deals with humans and robots solving crimes together, while walking the thin lines between their different societies ethics and political agendas. It's a wonderful series that i wished i'd read closer to the Foundation series, but i was both distracted by the Empire series and discouraged by the Foundation sequels by other authors, as well as the "I Robot" novel, which is a collection of 3 short stories, which can be considered a prequel to the Robot series, but is not really a part of this "epic" story. My suggested reading order:

1.The Caves of Steel (1954)
2. The Naked Sun (1957)
3. The Robots of Dawn (1983)
4. Robots and Empire (1985)

There are many more short stories, i haven't read them, so i am not sure which ones fit well with the "epic" storyline of these 4 novels. But these 4 novels do read as a wonderfully intriguing epic.