I never liked the "Arthur" Stories. PFFFFTTTTTTT men using swords, fall in love, get married and die. Not my kind of thing, but I did like the "Wizard side of things. So did my best to read about Merlin. During my "Quest for knowledge" I found a book by Marion Zimmer Bradley named "Mists of Avalon". What I liked about it is the fact that the whole story was not from Arthur's viewpoint nor Merlin's viewpoint (Which is the general views you get when reading such books), this was written from Morgana's viewpoint. I fell in love with the book. Read it probably 50 times (Since I got it) and is the story about the Lady of the lake. It is a very dark story, but the magic and drama involved in her life from childhood to where she becomes the Lady of the lake is fantastic. I loved it so much that my youngest daughter was named after her.
Several years down the line (reading the book probably twice a year), I found out there was a (UK) 3-part mini-series based on the book also called mists of Avalon. It was not available in my country, but I was able to import it. Still one of the best DVD's I own.
Recently finished "His Dark Materials (Books 1-3) again, and rewatched the 3-season series (Still have about 4 episodes left to watch of season 3)
Some do not like watching a series or a movie about a book since they say that much is changed. I take it as widening the perspective of the story. Giving different insights to the characters. I might not have liked a specific character in a book but might like him or her in a series/movie based on the same book due to actions they take that suddenly makes more sense visually.
My main problem with movie/series adaptations of books are that a lot of them are just bad. Same with adaptations of video games into movies/series and adaptations of movies/series into video games.
Though even if an adaptations is bad, they can sometimes still contain some elements of greatness. Case in point the best opening of a movie I've ever seen:
I don't remember a single thing from the rest of the movie because it was entirely forgettable, but that opening scene is amazing.