London — So much for Yankee ingenuity. Just when Americans thought they had claimed once and for all a corner on the snobbery-for-fun market, with their ''Official Preppy Handbook'' and ''Save-an-alligator-shoot-a-preppy'' bumper stickers, Britain has delivered a coup de grace: the social phenomenon called ''Sloane Rangers.''
The Ebury Press, in conjunction with Harpers & Queen magazine, has just published ''The Official Sloane Ranger Handbook.'' In case its essentialness escapes the reader at first glance, it is subtitled ''The First Guide to What Really Matters in Life.''
The book by Ann Barr and Peter York appears to be doing for Britain what ''The Official Preppy Handbook,'' that tongue-in-cheek, upper-class prep school sartorial guide, did for America. In other words, refining and defining those little marks of distinction of the well-heeled, well-connected British upper middle class - the how-tos of reading a person's nature in his neckties.
Yet this British publisher is flaunting the fact that there is life before preppiness. And that, they assert, is more proper than a club tie and your Harvard degree.
''Sloane Ranger,'' or SR to those in the know, derives from Sloane Square, one of the toniest of London neighborhoods, and the Range-Rover, the choicest of British country vehicles. The phenomenon was first spotted by Peter York in 1975 , when he recorded his initial sociological observations in the pages of Harpers & Queen magazine. His efforts to satirize social snobbery and make it acceptable were wildly successful. Other magazines and newspapers rushed to borrow the term.
Today references to Sloanes are as commonplace in the United Kingdom as are preppy labels in the United States. ''Let's go hunt up a few Sloanes after the theater,'' one young Londoner says. And with the advent of the official handbook, newspapers such as the Sunday Express have turned over whole sections of their Sunday magazines to further exploration of this social occurrence.
Yet, what really launched Sloane Rangerhood into fashion was not the handbook at all. Rather it was the Princess of Wales, then popularly known as Lady Di.
''The old Ranger Brigade looked like an endangered species at the end of the Seventies,'' the handbook states. ''But when Diana Spencer hit the lenses, she pepped up the Ranger wardrobe and boosted morale, reaffirming the Sloanes' looks and qualities but reinterpreting them for the Eighties. What the papers called the 'Lady Di Look' was actually pure SR.'' Somewhat tongue in cheek, the authors have dubbed the Princess the ''1980s' Supersloane.'' They have even borrowed her portrait for the book cover.
The crucial point of being Sloane, the guide intones, is to look as if you have land in your past, money in your present, and a bright future indeed. ''Sloane Rangerhood is a state of mind that's eternal,'' the authors decree. It also happens to be a state of mind that is unequivocably British and therefore extremely difficult for outsiders to crack.
This is bad news for foreigners - particularly preppy-prone Americans. Despite some comforting similarities to preppy rules of rightness - ''why it really matters to wear navy blue,'' for instance - even the starchiest American knows that he is at best merely a pretender to this throne of social etiquette. As if to prove its one-upmanship, ''The Official Sloane Ranger Handbook'' sells for $: 4.95 ($8), while the Preppy Handbook goes for about half that price.
In its 150-plus illustrated pages, the handbook chronicles all it takes to pass social muster. Everything from ''the crucial cuff links,'' to the right social functions (''a wedding is the second most important occasion, after Ascot''), to the right pets (''The Horse'' is the Sloane's sacred animal).
Should one wish to respond to this social cataloging in the correct SR style, the handbook chronicles even that. One can simply brush it off as ''just a bit of a giggle really.'' Or more stolidly assert that one would have to be ''complEEEtlimad'' to take such rubbish seriously.