There are several themes or characters or actions that seem to take place in all of her books:
Stories tend to be about several characters, although a few are given more weight;
One person always dies;
Themes of religion, love, good, bad predominate;
There seem always to be persons who struggle with temptation, usually sexual temptation, and who justify their transgressions to themselves either successfully or not;
There are "enchanters", people who draw others to them for no apparent reason;
There is a kind of humor usually. I've noticed that it tends to work like a shaggy dog story, a little like John Irving - the slow creation of characters and circumstances accumulate and culminate in some scene that is visually entertaining. Not cause for guffaws but usually a few smiles.
It is hard to like any of her characters completely.
In the Bell, I came to like the two central characters by the end of the piece, but I was often irritated by them and didn't fully take their sides until I felt they were finally becoming "good" people. In another book, I took to one of the characters until she had thoughts about where she was going, just before she died, that really pissed me off.
Murdoch tends to overspeak. Her characters are forever thinking, sometimes the same things over and over, and we are not given enough space to work out their thoughts because they are given to us. I feel this is a fault in her writing, that she does not leave enough for us to work out and wonder about.
Was a movie ever made of The Bell? It seems like a perfect story for a film. The visual nature of film would necessitate leaving out most of the mental hand-wringing, which I think would lead to a tight, good story that could be better than the book.