I guess I was intrigued by The Time of the Ghost because so much of it is actually drawn from her life. For my Adolescent Lit class, we had to do a report on an author--read three of their books and research their life and awards/accomplishments. In an autobiography, DWJ talks about how negligent her parents could be. She tells the story of how her sister tied her hair in knots in front of her face, hoping to get their attention, and how neither the mother or father even noticed. (One of the sisters does this in the book.) They were very busy running a boarding school for boys and the girls had to live in a shack and take care of themselves. It sounds like a story--but according to DWJ, it's true! The Time of the Ghost is almost entirely biogaphical--the parts that aren't fantastic, at least. I recognized so many things from what she had described of her childhood, and that alone held my interest.
I admit that the chicken sacrifices and strange doll god were quite pagan. But I had just finished Garth Nix's Sabriel so I was feeling pretty unfazed by dark magic. And despite the interest on a biographical level, I found the whole mystery--who the ghost really was, and the play back and forth between past and present--to be very fascinating. Also, the sisters' characters were very distinct (I thought the characterization was well-done, even if the sisters were not the most pleasant girls you've met in fiction).
I think that is one thing I find interesting about Diana Wynne Jones. Her main characters are decidedly human. She doesn't try to glorify them or make them overly good--they are petty and have faults and make mistakes and fight and she doesn't excuse them--that's just the way they are. Even so, they are not bad people and you like them. It is very interesting to me. Even Sophie in Howl's Moving Castle is a bossy sort of woman, bullying everyone around, but you still love her. And don't get me started on Howl. He is a slitherer-outer, just like Sophie says, and yet we still like him.
I liked Aunt Maria and Witch's Busines. I had read a lot of DWJ by then, and perhaps it tainted me into liking her even if a book is flawed (it is entirely possible that I am attached to her as an author and blinded by this, as sometimes happens). You didn't say what it was that you didn't like about these two. For myself, I just remember being entertained and thinking that her plots are always decidedly clever and her characters are always well-done, and therefore I liked them. I don't know about that Argus one, never heard of it.