What would you do if you lost, at one fell swoop, every one of your possessions? What if a thief were to come in and take not only your television and your jewelry but your dirty dishes, your underwear, your light bulbs, even your toilet paper? This is what happens to Mr. and Mrs. Ransome, the bourgeois, habit-bound couple in Alan Bennett's sharp new novella, THE CLOTHES THEY STOOD UP IN (Random House, $14.95).

It comes as quite a shock to them to discover just how much their lives have been controlled and defined by their objects, and when they are suddenly relieved of them the couple's reactions expose the irreconcilable differences in their characters: Mr. Ransome rigidly carries on as though nothing has changed, while his wife begins to feel rebellious twinges of -- dare she admit it? -- freedom and adventure. But then their paraphernalia is restored to them as mysteriously as it was taken away, and ''life returned to what Mrs. Ransome used to think of as normal but didn't now, quite.'' Their marriage, and they themselves, have subtly changed.

"The Clothes They Stood Up In'' was a best seller in Britain, where Bennett, the author of the plays ''Habeas Corpus,'' ''Forty Years On,'' ''The Madness of George III'' and countless other films and television shows, is rightly thought of as a national treasure. The book will probably not do quite so well here, for the traits personified by the Ransomes -- emotional constipation on the husband's part, an almost pathological diffidence on the wife's -- are English vices and not American ones. (Our own run on quite different lines.) But it is a witty, dark piece of work, a happy evening's read and a tantalizing mental challenge to those of us who, like the Ransomes, find their lives encumbered and their senses blunted by too much stuff.