Adaptations

I'll get this out there now . I generally hate adaptations of novels, yet I still invariably find myself watching them, and getting more and more annoyed as the film goes on. Why do I insist on doing this ? I have a sort of twisted faith that it may get better as it goes along - that rarely happens, or in some random and crazy way the director, producer and scriptwriters actually show 'so yeah, we um sort of maybe read the book, once, when I was 12 or something, abut this is what I thought it should be like' Those are the films whilst infuriating, somehow keep my mind ticking over for days and days.
Having recently rewatched Sally Potters 1992 film of Orlando,it again struck how much of a curious interpretation of events it was, compared to the novel. I liked the film, don't get me wrong, Tilda Swinton as Orlando has to be one of the most inspired castings, (I'm less convinced by Billy Zane , slimly little critter) who else could pull off the androgynous Orlando so well ?  But the film plays with the narrative and changes things.Whist I'm on my rant can someone please explain to me what that singing cherub is at the end ? It  baffles to say the least, and it messes with the ending, of 'The Oak Tree' it ceases to be the end of the circle. Does this make it a better story ? Or does it make it a whole new one ?