Beowulf was a Scandinavian hero who fought the monster Grendel and then had to hunt down Grendel's mother. Later in life, he slew a dragon that was attacking his people and he was mortally wounded during that battle. The poem that recounts his legend was written more than 1000 years ago in the old Anglo-Saxon language. And the deeds the legend grew upon are believed to have occurred during the 6th century AD - 400 years before the writing of the poem.
I've read a couple of translations of this ancient epic poem and found Heaney's the easiest to follow and understand. There's an excellent introduction and there are explanatory notes in the margins of the translation. So you're in with a chance of enjoying and understanding it. Unless you know what to expect it can be very confusing, because the original construction is unlike anything written today. There are places where other stories are embedded in the main story/poem and it's not at all obvious what's happening if you have no guidance. It can seem that the narrator has just gone flying off at a tangent, leaving you to wonder what's going on. Heaney solves these problems by making it clear what's happening all the way through.
If you haven't read Beowulf before and you want an easy and enjoyable translation, this is for you.