Forgotten, you say with the questioning look in your eye. Don't you teach it every semester? Don't high schools still require it as reading? My argument here -- and what I face every semester -- is that Beowulf is the most misread book I think there is. Okay, the bible probably tops it. Second most misread book, then.
If you Google Beowulf in search of an image of it you'll come up mostly with pictures from the Zemeckis' film, which I have already mentioned is utter pants. What that tells us is that most people when looking for something called "Beowulf" are looking for a crap film full of modern "twists" on the tale, cynicism about heroics and gross misunderstandings of the poem. Apparently the writers read the Heaney-Wulf, not the original. Heaney is a great poet, but his poem is not Beowulf.
Sadly, for many years I was one of those folks who dreaded the book. I took to heart Woody Allen's character's advice to Diane Keaton's Annie Hall on going back to college, "Just don't take any class where they make you read Beowulf!" I was all too willing to believe that it was something for laying down and avoiding.
Then my Swedish teacher at Harvard (where I was assiduously making use of my employee benefits, something a minuscule percentage of employees do) suggested I take the course "The Heroic Tradition in Northern Europe" with Stephen Mitchell. That course was the one-two punch that changed my life and made me a medievalist. We read Beowulf, Njal's Saga and The Völsunga Saga and my head exploded (in the good way). My first reaction was fury -- why did people keep me away from Beowulf all these years?! It was amazing! And why did no one tell me that books like the Icelandic sagas existed? They belong up there with Shakespeare and Austen. Flabbergasted, genuinely so. I am forever grateful to Mitchell (and have had the chance to tell him so :-).
Yet there's something to be said for being prepared to read Beowulf. Most of my students who "read" the book in high school seem to have had it taught by someone who hated it as much as they end up doing. I like to think I rescue a few of them from the errors of their ways. The key is understanding the culture from which it arises: a Christian culture that nonetheless not only looks back at a heroic past, but embraces much of it while trying to convince themselves it can jibe with orthodoxy.
The Anglo-Saxons, after all, had to imagine that Christ climbed up on the cross, because they had to see that hero acting the way they expected their leaders to act. The poem is written down in a time when the tensions between the English (descendants of the Angle, Saxon and Jute Germanic tribes who invaded the Celtic Britons after the Romans left) and the Viking kings who had ruled parts of the country off and on for some time.
Consider how odd it is to have a poem written in English and copied down by monks at a time when a Danish king might be ruling England -- a poem that valorizes the ancient pagan past of Danes and Geats and Swedes and Frisians. I could go on and on (and do, regularly) but consider also, its narrative voice, which is consistently Christian and yet admiring of these often brutal kings of the past. The opening lines which set up the poem tell us Scyld Scefing, who intimidates his enemies and steals their wealth, is "a good king." This isn't modern American Christianity, which the medieval world would mostly find appalling and wrong-headed, it's their own brand of heroicism, largely situated in the stories of the old testament, not the new.
It's a story about heroes and monsters, first and foremost. Like all good stories, however, it touches on many themes: the mysteriousness of the vast world, the difficulties of ruling, the pride of the warrior, the use of public performance (we don't hear anyone's thoughts, everyone is conscious of speaking before a crowd), the treacherousness that can grow in those closest to your heart and the brutality of life. While Anglo-Saxon poetry concerns itself seldom with women or romantic love, the two central women, Wealtheow and Grendel's unnamed mother, show the respect that women held in the Anglo-Saxon world. Wealtheow's wise words, when her husband goes overboard thanking the champion, seem to echo in Beowulf's mind years later when the people urge him to take the crown, but he defers to his king's young son as tradition dictates. The Danish queen would be proud.
I urge you to learn Anglo-Saxon and read it in the original: there's no comparison. Translation, however, is going to be the way most people encounter it. So I recommend these two as the best: Liuzza's as the most accurate, Crossley-Holland's as the most engaging with nonetheless good accuracy.