AGATHA CHRISTI BEGAN IT ALL IN 1920 with a nice quiet little mystery novel called The Mysterious Affair of Styles, and within its pages, she gave the world one of its most enduring, if not endearing, detectives, Hercule Poirot, an ingenious, egocentric little man who solved murders, he said, with the little grey cells in his brains.

In her first book, Agatha said of him: “He was hardly more than five feet four inches but carried himself with great dignity. His moustache was very stiff and military. Even if everything on his face was covered, the tips of moustache and the pink-tipped nose would be visible. The neatness of his attire was almost incredible; I believe a speck of dust would have caused him more pain than a bullet wound. Yet this quaint dandified little man, I was sorry to see, now imped badly, had been in his time one of the most celebrated members of the Belgian police.”

Hercule Poirot made his way into thirty-three of her novels, one play, and more than fifty short stories. In time, she came to detest his arrogance, confiding in her diary that she found him to be “insufferable” and referring to the celebrated sleuth as “an egocentric creep.”

She much preferred Miss Jane Marple, based on her grandmother. As she said, “Both Jane and Gran “always expected the worst of everyone and everything, and was, with almost frightening accuracy, usually proved right.”

For Agatha Christi, beginning a new novel, she said, was three or four weeks of agony, pain, and despair, a period when she could not force herself to write a single word. She said it was like being possessed with paralyzed hopelessness.

In her first novel, she wanted to base her murderer on an acquaintance but found she couldn’t. She said that not even in her imagination could she envision him ever murdering anyone. So she kept her notebooks close at hand and wrote down descriptions of characters by watching people in trams, trains, and restaurants. Everyone was a potential murderer. Everyone was a potential victim.

Agatha wrote with simple, every day language, and she relied heavily on dialogue. Plots, she pointed out, just came to her in the oddest of places, usually out of the blue, and would rattle around in her head for long periods of time. As she said, it was always quite strange to “feel a book growing inside of you, building up all of the time.”

Agatha Christie always began with the same writing process. She would decide on the method of the murder. She would pinpoint he murderer. She devised the motive. And finally she allowed the characters to wander into her consciousness, and, of course, those characters, especially the suspects, were given motives, as well. She kept her ideas scribbled down in a notebook, but, alas, Agatha had a bad habit of losing her notebooks.

Her formula, at least for her time, was a successful one. Her novels have sold roughly four billion copies, and her estate claims that her works rank third among the world’s most widely published books – behind only William Shakespeare and the Bible. Her novel, And Then There Were None became her best seller with a hundred million copies sold.

These are the insights she has left for writers:

• On writing a book. You start into it, inflamed by an idea, full of hope, full indeed of confidence. If you are properly modest, you will never write it at all, so there has to be one delicious moment when you have thought of something, know just how you are going to write it, rush for a pencil, and start buoyed up with exaltation. You then get into difficulties, don’t see your way out, and finally manage to accomplish more or less what you first meant to accomplish, though losing confidence all the time. Having finished it, you know it is absolutely rotten. A couple of months later, you wonder if it may not be all right after all.

• There is a right length for everything. I think myself that the right length for a detective story is fifty thousand words. I know it is considered by some publishers as too short. But if your book runs to more than that, I think you usually find that it would have been better if it had been shorter.

• When you begin to write, you are usually in the theories of admiration for some writer, and, whether you will or no, you cannot help copying their style. Often it is not a style that suits you, and so you write badly. But as time goes on, you are less influenced by admiration. You will admire certain writers, you may even wish you could write like them, but you know quite well that you can’t. If I could write like Elizabeth Bowen, Muriel Sparks, or Grahame Greene, I should jump to high heaven with delight, but I know that I can’t, and it would never occur to me to attempt to copy them. I have learned that I am me, that I can do the things that, as one might put it, me can do, but I cannot do the things that me would like to do.

• On what she does with an idea: Toss it around, play tricks with it, work it up, tone it down, and gradually get it into shape. Then, of course, you have to start writing it. That’s not nearly so much fun – it becomes hard work. Alternatively, you can tuck it carefully away, in storage, for perhaps using in a year or two year’s time.

• On whether real people inspire her characters: I invent them. They are mine. They’ve got to be my characters – doing what I want them to do, being what I want them to be – coming alive for me, having their own ideas sometimes, but only because I’ve made them real.

• On Settings: You don’t invent your settings. They are outside you, all around you, in existence – you only have to stretch out your hand and pick and choose.

• I never realized what a terrible lot of explaining one has to do in a murder.

• Imagination is a good servant and a bad master.

• Every murderer is probably somebody’s old friend.

• I’ve always believed in writing without a collaborator, because where two people are writing the same book, each believes he gets all the worry and only half the royalties. 

• I specialize in murders of quiet, domestic interest.

Agatha Christie, during World War II, wrote, she said, the last cases for Hercule Poirot, Curtain, and Jane Marple, Sleeping Murder. The manuscripts were placed in a bank vault and were to be released only after her death. She got tired of waiting, and both novels were released in 1974.

In Curtain, she did what she had wanted to do for a long time. Agatha Christie killed off her insufferable little egomaniac, Hercule Poirot, at Styles. She would have nothing more to do with him.

He was the only fictional character to ever have his obituary printed in The New York Times.