I got this some time back and skimmed it rather casually; but this weekend I have taken a short break from Shakespeare to read it thoroughly. It is a tremendous achievement. I think I had read two other adaptations of the epic poem, one probably by Roger Lancelyn Greene, the other a re-telling of the story from Grendel's point of view by John Gardner. I also saw Julian Glover recite most of it on stage in Belfast many years ago. I haven't seen the recent film as we so rarely get to the cinema.
Heaney has tried to retell the poem in its own terms, and his recasting of the poet's original imagery is vivid - we can almost smell Grendel and his mother, and Smaug's hoard seems a pale reflection of the dragon which brings about the tragic end of Beowulf's life. (Of course, Tolkien was one of the leading Beowulf scholars of the twentieth century, and there are entire sections of The Hobbit which have practically been copied from here.)
Apart from the gloriousness of the overall narrative, three things struck me, two more or less for the first time. First, it is actually an explicitly Christian poem, if in a rather weird way. Hrothgar commissions Beowulf to fight Grendel in terms that sound like God the Father sending his Son to defeat evil. Although the setting is the pagan past, the writer makes frequent allusions to Judeo-Christian concepts of destiny and virtue; the only explicitly non-Christian characters are the monsters.
Second, and related, there are numerous reflections on what makes a good king - not just the narrator's own oft-repeated phrase, "þæt wæs god cyning!" but also discourses from various characters in the midst of the action. It practically makes Beowulf a treatise on political science, along with its many other features.
Third - and this was the point I had noticed on previous skimming of the text - is the occasional diversion of the narrative to tell some other story only tangentially related by theme or personality to the main narrative. I'm going to stick my neck out and say that it doesn't work well for me, and I can't believe it worked well in oral presentation (I can't remember, but I'm pretty sure Julian Glover skipped those bits in his stage show). I am inclined to think that the compiler of our version used the opportunity to fold in some other bits and pieces of epic poetry which he or she had handy, so that they would not be lost to posterity.
Anyway, this is (quite literally) epic stuff.