RADIO / Judging a bookshop by its cover: Robert Hanks reviews Drif's guide to the Northern Line and P D James's Cover Her Face

BECAUSE reading books is, or can be, an intellectual pastime, it's easy to think that collecting books must be, too. In fact, your genuine bibliophile is impelled mostly by a batch of primeval instincts. At bottom, there's ordinary acquisitiveness, a primeval hoarding instinct that some squirrel-like ancestor left imprinted on our genes. This is, in turn, channelled through a primitive materialism that believes minds work through objects. Just as a Dyak might believe that a photograph can contain his soul, or an American Indian might eat a bear's heart so that he can have the bear's courage, so book-collectors feel, at some superstitious level, that by simply owning a book - reading it is irrelevant - they can possess the knowledge it contains.

They're wrong, of course. Certainly, it's hard to see the civilising influence of a lifetime in the manners of Drif Field, author of a series of eccentric, shoddily laid out guides to second-hand bookshops around the country, and now presenter of Drif's Guide to the Northern Line (Radio 4, Tuesday), a special edition of Down Your Way with the unspoken subtitle Up Your Nose.

Drif conducted us from Wimbledon to Edgware, a route that he believes is the present-day, extended version of Charing Cross Road, handing out small theories about the book trade (the best bargains are in the window) and generally annoying bookshop owners. He prizes courtesy above all, in other people at any rate: for himself, he can't do it straight, only in French - a cheery 'Au revoir' here, a 'Merci beaucoup' there. At one socialist-leaning bookshop, run by a former leader of Haringey Council, he pondered the apparent prevalence of the Left in the second-hand trade: in the course of the discussion it was established that while Drif himself may be socially gauche, politically he stands to the right of, well, Genghis Khan is his own current version, though in early editions of his guide he apparently used Adolf Hitler as the yardstick.

The main problem with Drif was that he liked the sound of his own voice too much. Bores can make for good entertainment, but you have to be able to laugh at them. Collusive comedy about bores - cf Les and Robert (Radio 4, Saturday), a mock- thriller serial about two intolerably dull men from Lancing - is swimming in mud.

Still, if Drif wasn't a congenial guide, the trip wasn't entirely wasted. He didn't pursue issues with much tenacity, but he did start up a few. The most intriguing episode was a conversation with an 80-year-old lady who specialised in selling books on 'True Crime'. Drif wondered if she ever worried about the kind of people who read her books, but she said that apart from the 'weirdies', who call up looking for illustrated accounts of autopsies and the like, she thought that the desire to read about crime - a nice domestic murder, nothing too kinky - was so natural and so widespread that she had never bothered to think about it. 'I believe that the world would be dreary if there were no crime. I can't imagine a world without crime. Can you? Can you imagine heaven?' Drif giggled that he didn't think heaven would be crime-free.

Crime-infested heaven is the staple of the detective story, at least in England. Typically, an English murder will take place among the upper-middle classes in a peaceful rural setting - the crime's horror resting, for the reader, in the incongruity as much as the fact of death. The beauty of Cover Her Face (Radio 4, Wednesday), P D James's first crime novel, now 30 years old and dramatised in four parts - is that it knows how unrealistic this pastoral scene is.

In this story, James seemed to spoof the typical Agatha Christie setting and cast. The house where the murder takes place, Martingale, is an Elizabethan manorhouse in an East Anglian village: almost the first thing we hear is that 'even in the Fifties it was an anachronism'. There's the local vicar, and the doctor, and the faithful retainer (an elderly woman sexually attached to her paralysed master). There's also Miss Liddell who, like Miss Marple, trains girls for domestic service - but Miss Liddell's girls are unmarried mothers (the victim, Sally Jupp, is one of these women), and she herself is sexually repressed and mildly hysterical.

Neville Teller's adaptation abridges the whole thing drastically, so that we're left with the bare bones of cliches at times ('You deserve to be dead,' old Martha mutters at Sally), but you can still sense a clever, slightly rebellious reworking of the old formulas. It's just like the Sixties all over again.