Flannery O'Connor is often billed as a Southern writer, or as a Catholic writer. But, however helpful, these are confining terms. For she was an artist of the most exacting and universal perception….

Almost a dozen books and innumerable articles have been published since 1964 on her small but intense oeuvre…. But far the longest and most important posthumous publication is that of her letters, a collection of more than 600 pages spanning the years 1948–64. For wealth of anecdote and intellectual variety and emotional depth, The Habit of Being too will prove an incomparable American work.

Its keynote is joy. Confined to hospital in 1950, with what was then diagnosed as "acute rheumatoid arthritis", she wrote: "I have been reading [T. S. Eliot's] Murder in the Cathedral and the nurses thus conclude I am a mystery fan." But the nurses were right. She was a "mystery fan"; and she confronted life's...