AGATHA CHRISTIE liked to make raspberry jam. She enjoyed doing crossword puzzles and going to the traditional English pantomine theater. She adored venturing out on grueling archaeological digs with her second husband, Sir Max Mallowan. There is every evidence that she had a fondness for mildly scatological stories. As a young woman she loved to dance and reportedly did a mean tango. As a well-to-do matron she indulged her passion for buying houses and decorating them. But more than anything else in her long life, Agatha Christie liked her privacy.

As a result of her own posthumous Autobiography and a recent Festschrift comprised of contributions by fellow-travelers in crime we have some idea of how she saw herself and how others saw her. Still, there is one problem which has plagued Christieites and sensation addicts alike for years: what was going through her mind when she disappeared for 10 days in 1926, leaving behind a daughter and a philandering husband and precipitating a hue and cry throughout the whole of England?

WHERE IS MRS. CHRISTIE?* SLENDER CLUES. 15,000 PEOPLE SEARCH . . . BLODDHOUNDS FAIL. 100 REWARD. NOVELISTS HUSBAND INTERVIEWED . The plot unfolded in the headlines, and each day ticked off another chapter in the real mystery tale which turned out to be not quite as tricky as one of Christie's own. Where was she? Well, she was registered (rather oddly, to be sure, under the surname of her husband's mistress) at a large hotel in the spa of Harrogate. But she was certainly not skulking around in dark glasses: she had on more make-up than usual and her first night there did the Charleston in the lounge to "Yes, We Have No Bananas."

All very peculiar, and today it would be perfect material for a pop psychoanalyst writing in the pages of Cosmopolitan . But at the time it was shocking and confusing (as much so, apparently, to Christie as to anyone else), even decried as an unsavory publicity stunt after the Christie family blamed the whole affair on a fishy-sounding attack of amnesia.

Just how interesting is all this in 1978? Since Christie is one of the best-selling writers in history, her strange story might have a certain commercial value, overlaid as it is with the art deco patina beloved of nostalgia fanciers. In other words, enough commercial value, along with a couple of bankable stars, to get a glossy treatment in Hollywood and an equally glossy novelization of the filmscript.

This brings us to Kathleen Tynan and Agatha , her new "novel" about Christie's 1926 disappearance. Christie would have loathed this book because it tramples on her intimate feelings under the guise of sensitive probing. She would also have hated it for the same reasons she would have hated a bad dancing partner: it simply has no sense of rhythm as it moves clumsily from episode to episode. Tynan is obviously intelligent but it was not intelligence that was needed to make this work. What was wanted was affection for the redoubtable Dame Agatha and her world, not so much the world she lived and breathed in but the wonderful cozy world she wrote about. What we get instead, as Tynan attempts to recreate and dissect those 10 days in Harrogate, is something like "An Unmarried Woman" starring the young Margaret Rutherford.

After 1926 Christie kept on writing, got divorced, and got married again, this time happily and for ever after. She rarely granted interviews and when she did it was with the sly manipulativeness of a Nabokov. She allowed a hagiographic study of her life to be issued by her own publisher in the late '60s. Now Gwen Robyns, a genteel hack, has gone that earlier study a bit better.

Robyns talked to a lot of people, some peripheral and some central, and what she delivers is a gushing book full of painful prose and an egregious number of errors. But compared to Tynan's book, Robyns' is by far the better buy, even at a dollar more. It's chockfull of anecdotes and amusing tales of Christie's crotchets and kindnesses.

It is easier to decide what to think about the Robyns than it is to know how to feel about the Tynan. A public person is entitled to private distress, though it practically never happens that way. Tynan makes a convincing case for her insights into Christie's emotional crisis; it's only that the rest of it is so artificial, including a foolish bit of near-mayhem. And the insights Tynan does color in so meticulously are the same stale ones Robyns hears when she can find anyone to discuss the disappearance with her.

Will we read Agatha because it is about Christie, because we're on a fiction jag, or because old scandals never cease to pique our imaginations? If the last is true, perhaps someone will write Dorothy , for the creator of Lord Peter Wimsey, Dorothy L. Sayers, had an illegitimate child and never revealed the identity of the father.