I just finished re-reading Grendel.
When I was a high schooler who loved Beowulf (there are dozens of us, dozens!), it was a thrilling book, as seeing things from a villain's point of view was novel. When I'd tell people over the years how much I liked Grendel, I would get a few raised eyebrows. Re-reading it decades later, I can see why.
In his introduction, Gardener said he wanted to structure it as Grendel interrogating a dozen different philosophical world views before finally meeting his end at Beowulf's hands. Weird choice, but it could be OK.
Instead, it's mostly a short novel of beautifully written descriptions of fantasy Denmark, complete with language that apes that of Beowulf, like "swan-road" and similar constructions. And then that's punctuated with a freshman philosophy student wandering onto the page and screaming a synopsis of various philosophies at the reader.
It's OK when it's The Dragon being nihilistic and encouraging Grendel to villainy, because nothing really matters LOL, but when it's a random Danish peasant going on for several pages about philosophy, it pulls the reader out of the fiction in return for ... I don't know what. I'm not sure what Gardener was going for here.
I could easily see someone like GRRM taking on this task, but in his hands, he would express this with naturalistic language or action (think Littlefinger's "chaos is a ladder" speech in Game of Thrones) and accomplish what I think Gardener was going for here and make it compelling.
Instead, it feels like Gardener had what he thought was a clever idea and couldn't be moved to integrate it better into the fiction. (Beowulf, when he appears, sort of does this, whispering to Grendel that the rational modern world will mean the end of monsters like him, although it's still somewhat clumsy in execution.)
This all frustrates me, because when we're not getting Philosophy 101 shouted at our faces, the rest of the book is really good, with Grendel tormenting the greatest of the Danish heroes by not killing him and refusing to battle him, completely destroying the hero's morale over a period of years by making him irrelevant. And we see Hrothgar marry the young sister of a rival lord, and her being torn between misery and duty. And then Hrothgar takes in the son of one of his dead brothers and everyone in the novel sees that, eventually, he'll attempt to kill Hrothgar and plunge the weakened realm into war.
So all of the pieces are there, but Gardener kind of ruins it with Danish peasants yelling collegiate philosophy at each other.
I re-read this because they're apparently going to make a movie of this soon. I'm not sure how they will, unless they strip out the philosophy and just Game of Thrones it, which would be good. My suspicion is that it's just going to be a Danish Shrek, though.