It's a good read for historiographies, but I'm sure ancient historians have gone past some of his theories. Nevertheless, it's still regarded as a classic.

If you want more modern books, check out: Peter Brown's World of Late Antiquity and Peter Heather's The Fall of the Roman Empire

There are different theories on the fall, you could probably go through an entire library of them. I just picked selections I had from class, as I think these were more readable.

I would say it's worth it for the language even if the field has moved way past his ideas. He's got a great style, dramatic, even sassy, and so much doom and gloom you'll wonder why Fox News doesn't just read it on air replacing the proper nouns.

Gibbon starts early, with Augustus if memory serves. There aren't too many histories I can think of with such a large scope. If you want some good reading on the Roman Empire I suggest going to the source: Suetonius or Tacitus (whose style Gibbon emulates). For later stuff you can do the untrustworthy but entertaining Historiae Augustorum. If you want a long narrative history instead of biographies you can pick up Cassius Dio and Ammianus Marcellinus.