Spark's novels are short and very short. There is no excess of detail. And yet they take you in strange and curious journeys, and are always somewhat mysterious. She always played with questions of fate, free will, narrative and artifice, and (as Brock Clarke brilliantly points out in an essay for Believer Magazine) the God-like qualities of the author. And, they often have a vaguely auto-biographical feeling to them. My other favorite novels, Loitering with Intent and The Comforters (her first novel, and not well regarded, though I really enjoy it), were both about female authors. The Girls of Slender Means about young women in a boarding house in London during WWII. I never felt like I was reading Miss Spark's life, rather, I felt she knew intimately what her characters were going through. This immediacy and intimacy made them all the more strange and lovely.
Spark's own autobiography, however, is all but devoid of personal information. Of her conversion to the Catholic faith when she was an adult, she said simply "It was everything I had ever known to be right" and nothing more. She is blunt about her marriage, and speaks very little about her son. It is called Curriculum Vitae--a fitting name, for it speaks more of the education of live than the living of it. It's excellent, in its own way, but I finished it without any clear idea of who Spark really was.
Enter Martin Stannard and his new biography of Muriel Spark just released here in the US last week. I've only read the first chapter, so I can't give a real recommendation (though I can say that I don't like his style very much). The reviews have been pretty good all around (I've linked to them below). I found Maud Newton's most helpful.
Review by Maud Newton: "Wit Precision, Uppers and God"
New York Times: Dwight Garner and (her New Yorker editor) Charles McGrath
You can read an excerpt of the book (chapter one) here.
Also: James Wood on her last novel, The Finishing School
And Ms. Newton has a wonderful post where she lists the first lines of nine of Spark's novels.
Spark lived till 2006, seeing the internet age. In fact, she had two "diaries" published on Slate in 1996 (pre-blogging era). For a portrait of the artist at the end of her life, check them out here and here.