Why second-hand bookshops are just my type Booksellers tell stories that they regard as tall when they are in the mouths of others of their trade: they are a jealous and envious lot. But they all say that libraries around the country are disembarrassing themselves of 17th- to 19th-century books because, rarely consulted, they are deemed to waste space that could more usefully be devoted to computer stations and multiple copies of Dan Brown, much in demand. Certainly, those of us who like ancient books on arcane subjects have noticed that many of our purchases emanate from institutions of learning. It makes no difference that Mrs Theobald Smedley-Wilkins left Lead Poisoning in the Later Roman Empire to an institution in perpetuity in memory of her late husband, Alderman Theobald Smedley-Wilkins. The librarian takes his revenge upon the now redundant work by stamping it sadistically with a large and ugly "withdrawn," thus successfully reducing its resale value. This means that those of us who would like to leave books to public institutions as being exceptionally rare or even unique now think twice about doing so. Customers of second-hand booksellers, such as I, are also a rum lot. What kind of person spends two-and-a-half hours in a shop and then havers indecisively over whether he really wants a copy of Augustine Birrell's (unjustly) forgotten essays marked at £3? If he fails to buy it, he will regret it the moment the shop has closed or he can't get back to it. If, on the other hand, he (and customers are almost always he) buys a book that his wife will find outrageously expensive by comparison, say, with a pair of shoes, or even a single shoe, he will ask the bookseller to rub out the price. All booksellers are so familiar with this pattern that they are ready with their rubbers even as their customers buy. Browsing among the shelves is rewarding in a way that surfing the internet (the largest second-hand books website searches through 140 million volumes for sale, or says it does - I haven't counted) can never be. Of course, if there is a particular book that you want urgently, the internet is a wonder: you type in the title, you pay by credit card, the book arrives the next day. There is no need any longer to resort to the bookfinder, that strange professional searcher after needles in haystacks, who guards his sources more jealously than any journalist and, I suspect, would not reveal them under torture. But serendipity is the greatest pleasure of browsing, and there is no substitute for being able to hold the physical book in one's hand. Among other things to be found in books are the markings of previous readers. When I first started buying antiquarian books I rejected those that had been marked, but now I find the markings sometimes more interesting than the books, and certainly revealing of the byways of human psychology. There are, for example, those who seem to read hundreds of pages with the express purpose of finding the single spelling mistake or misprint contained in them and underlining it, putting a triumphant exclamation mark in the margin, as though finding the error established their intellectual superiority to the author. Of course, they attribute all errors to the author and none to the printer. Then there are the underliners. The majority of these rarely get past the first chapter or two; some underline things so banal - Smith then went to London, for example, or The snow fell in flakes - that one wonders what kind of mind wants to commit such things to memory. Philosophy books of the Forties and Fifties, meanwhile, tend to smell strongly of tobacco. The joy of finding something that one did not know existed, and that is deeply interesting or connected in a totally unexpected way with one's intellectual interests of the moment, is one of the great serendipitous rewards of browsing, and one unknown to those who take a purely instrumental view of bookshops, leaving them the moment they discover that they do not have the very book that they want. As for us aficionados, the strange thing is that one is guided by a kind of instinct to the right shelf. For example, in Manchester recently I found a small bookshop with so little stock that I wondered how it survived. For some reason I picked from the shelf a slim paperback entitled Making Sense of the NHS Complaints and Disciplinary Procedures - an illustration of an important literary principle, namely that there is no subject so boring that no one has written a book about it. This little book had so many bullet points that one felt one's brain had been attacked by a Maxim gun; in the foreword, Sir Donald Irvine, erstwhile president of the General Medical Council, wrote the following one: "The early recognition of dysfunctional doctors, adequate public protection, and the chance of effective mediation before damage dependent on sound local self-regulation in which doctors know what their duties and responsibilities are, and how to make the system work." Why on earth did I hone in on this book, so dull and tedious? There was a slip of paper in the book. It was a review copy, and had been sent out by a medical publication to a doctor for review. The doctor in question was Dr Harold Shipman, and the book had obviously been read thoroughly. I bought it for £5, not as a memento mori but as a reminder of the irony of human existence. The Pleasure of Thinking" by Theodore Dalrymple (Gibson Square) is available from Telegraph Books at £11.99 + £1.35 p&p. 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