Agatha Christie (1890-1976) is one of the world's bestselling writers; only the Bible and Shakespeare have sold more. The doyenne of mystery writers, Christie wrote more than 100 novels, plays and short-story collections. Her characters Miss Marple and Hercule Poirot are icons in literature. Her work remains popular, with a new star-filled movie version of "Murder on the Orient Express" released last year. Her play "The Mousetrap" has run in a London West End theater for 68 years, with more than 28,000 performances.

It's not surprising that her life was fascinating. She traveled frequently to Iraq with her second husband, an archaeologist known for his work at Nimrud near Mosul. But even more intriguing to anyone who loves a mystery, she disappeared for 11 days in 1926 — something that remains fully unexplained to this day.

Laura Thompson is the latest writer to assess Christie's mysterious life. She is the author of two other biographies, including "The Six: The Lives of the Mitford Sisters." More important, she was granted access by Christie's grandson to the rich sources stored away in drawers and suitcases at the writer's estate in Devon — correspondence, writings, cuttings and "mere scraps of paper."

Thompson is a sympathetic yet objective biographer. This large, eminently readable and well-­documented book follows a generally but not strictly chronological account of Christie's life, and it is laced with snippets from Christie's novels where Thompson saw parallels to the writer's life.

Born and raised on the southwestern coast of England, Christie's class was middle, tending toward upper; for Agatha, her happiest days.

As a young woman she had many suitors, but with the outbreak of World War I she chose, perhaps too quickly, to marry Archie Christie, who soon became a war hero. Their marriage produced a daughter, Rosalind, but when Rosalind was 7, two things happened: Christie's mother died, and Christie's husband professed love for another woman. That December, Christie disappeared for 11 days.

Thompson covers the disappearance uniquely, writing in a voice that Christie might have had while experiencing that strange time. Thompson also disputes the accounts of Jared Cade in "Agatha Christie and the Eleven Missing Days" (1998), noting his book was filled with "fundamental naughtiness" and citing several instances of spurious reasoning.

In any case, the disappearance changed Christie forever: Her marriage fell apart, she became more independent and, Thompson argues, her persona as an author was formed.

Christie's mid- and later life was devoted to her work and to a happy second marriage that took her to Iraq and Syria, further stimulating her writing. It was also burdened with decades-long disputes with tax authorities which, as Thompson relates, seemed unfair but also gave her more incentive to write.

In the end, Agatha Christie is portrayed here as a driven, at times vulnerable, woman who found what she wanted and needed to do with her life. For that, and for Laura Thompson's new biography, we are all richer.

Jim Carmin is a member of the National Book Critics Circle. He lives in Portland, Ore.

Agatha Christie: A Mysterious Life
By: Laura Thompson.
Publisher: Pegasus, 534 pages, $35.