I don't know about "fun..."
At 1,300 pages, it was quite a slog when I read it through for the first time back in college. My current copy is a nice hardcover combined edition. My first set was a couple of used paperbacks.
"Asimov's Guide to Shakespeare" is also pretty good.
Does anybody else remember all his great short science articles?
Oh, I hear he dabbled in SF too... ;)
