Invisible Ink: No 191 - The Rivals of Agatha Christie - Features - Books - The Independent Agatha Christie's books continue to expand in sales, with squillions sold around the world each year - they're apparently huge now in India. Who can explain the enduring popularity of the whodunnit? WH Auden pointed out that traditional crime fiction rewrites the creation myth; the snake is expelled and Adam and Eve return to a state of innocence. Or rather, the snake, having been found guilty, stumps off to the library and shoots itself. What no one has adequately explained is why Christie leapt over her rivals in sales - and rivals there were aplenty. Patricia Wentworth was born in India but settled in Surrey, where she wrote 32 whodunnits. Her heroine was a retired governess-turned-private eye, the incorrigibly nosy Miss Maud Silver, a character not unlike Miss Marple, who insinuated herself into upper-class households and meddled until she unmasked murderers and restored order. There are sinister undercurrents in the Wentworth books that often reflect the hypocritical morality of the period. Her cases have recently resurfaced as ebooks. Elizabeth Daly was purportedly Christie's favourite mystery writer, and it's easy to see why. She takes the bloodless whodunnit to an extreme distance, turning every crime into an analytical puzzle that could be viewed through field-glasses. Her bibliophile detective is the literary and sophisticated Henry Gamadge, a New York consultant who authenticates rare books, and if the rest of her cast tends to be sketched in, her period NYC settings are superbly evocative. Wales-born Dorothy Simpson started later with the rural Inspector Luke Thanet, as did Anthea Fraser, whose Shillingham police novels sport titles based on lyrics from the English folk song "Green Grow The Rushes, O." Hazel Holt created the charming Mrs Malory series, but perhaps Caroline Graham turned out to be Christie's chief rival, even though her Chief Inspector Barnaby series has only run to seven volumes. A TV series based on her books was originally adapted by Anthony Horowitz to become Midsomer Murders, the ghastly long-running series involving convoluted crimes in picturesque fictional Somerset villages. International success brought longevity to the show, meaning these thatched hellholes developed a murder rate twice that of the Bronx in the 1970s. None of which explains why Christie so soundly thrashed her rivals; perhaps her neatly structured but skeletal novels remain open to reinterpretation, and are undemanding diversions, like crosswords, or she overwhelmed by sheer ubiquity.