This week, I found myself in the most distinguished peepshow imaginable. It was at Sotheby's where, today, they're holding an auction of the most astonishing literary stuff I've ever come across.

This week, I found myself in the most distinguished peepshow imaginable. It was at Sotheby's where, today, they're holding an auction of the most astonishing literary stuff I've ever come across.

There's a copy of Darwin's On the Origin of Species, inscribed to his daughter Henrietta, that's as rare as dodo dung. There's a first published edition of Alice's Adventures in Wonderland signed (typically) to the nine-year-old daughter of the Oxford Professor of Political Economy. There's a previously unknown photograph of TS Eliot in the 1920s, posing beside a car in New Hampshire, wearing a very Gatsby-ish racing cap, shorts and woollen knee-socks. A picture of TS Eliot's knees! You can't get that kind of merchandise on the open market for a queen's ransom.

I spent a blissful 90 minutes in Sotheby's Book Room, perusing the "lots", amazed to find that, if you asked the attendants nicely, you could hold in your shaking hand the first edition (1726) of Gulliver's Travels; you could also pick up a proof copy of The Fellowship of the Ring, and try to resist hurling it across the room in disgust...

As I wondered around this bookish El Dorado, I was conscious of looking a little... suspicious. As if my presence there wasn't entirely... innocent. And I wasn't the only one. A bearded guy in his twenties was doing a lot of hovering, faking interest in the Quaker marriage certificates on the wall, trying to work up the courage to say "Hi - could I have a quick look at lot, er, 201?". Clearly he was only here for the smut.

You probably know all about the Joyce-Nora letters - the exchange of 10 yelpingly explicit missives in December 1909, when James Joyce was in Dublin and his beloved Nora Barnacle was home in Trieste. It was the 1909 equivalent of telephone sex. Most of these letters were published in 1975. The one at Sotheby's wasn't. It's been lost for years and no Joyce scholar has seen it. It was the crucial letter that started off their masturbatory frenzy of impassioned urgings. It's worth at least £50,000.

My interest in the thing was, I need hardly say, entirely academic, unlike the prurient voluptuary in the beard. I engaged one of the auction house's literary experts in, ooh, several minutes of bookish chit-chat, and when he said, "I suppose you want to see the letter", I could hardly say no. But there was a snag. Stephen Joyce, the writer's combative grandson, is dead against the auction house selling the letter and complained bitterly about it in the Sunday papers. Now he has forbidden the Sotheby's people from showing the contents to anyone except serious bidders - and definitely not to the prying eyes of journalists.

So there followed a few minutes of surreal fencing as I strove to read the letter, and the Expert strove to conceal its contents. " My darling little blackguard..." it began, before promising to administer the shagging of a lifetime. "Sorry, no, you can look but you can't read it," said the man, laying a buff envelope over the rest of the page. "Here at the end, notice how the handwriting gets suddenly larger" (" You are mine!!!" yelped the letter in a climax of screechmarks, " My schoolgirl!!!") "Joyce ends by asking 'Heaven to forgive his madness'," continued the Expert, nonchalantly sliding his buff-envelope shield over the top half of the page, covering up a flurry of words like "mouth" and "filthiest".

It was a ridiculous bit of peek-a-boo tantalisation. I felt like I'd come to Bond Street for a three-minute Soho peepshow. How shocking to find that we serious fans are just as avid for dirt as any freeze-framing teen viewer of Scary Movie 3.

Cocktail parties and shagpiles

There's more to literary memorabilia than dirty correspondence. There are things called "associations", personal items which weren't directly concerned with the author's creative processes but which have acquired a sheen of glory by being caught up in the author's life. So people will be bidding at Sotheby's for Joyce's spectacles, and for the leather bracelet to which he attached a silk pouch containing a folded-up telegram from Nora displaying the single word "Si".

We can only wonder what she was saying "Yes" to ("Please may I write feverishly rude letters about your bottom?" would be a fair guess), but her James wore the telegram close to his skin every day for the rest of his life. I made a couple of discoveries myself in the Book Room. In the first edition of Ulysses (inscribed to James's brother Stanislaus), between pages 334 and 335, I found an invitation to a cocktail party from Leonard Unger, the US political adviser, to Stanislaus and his wife. Can it be that the stiffie acted as a bookmark, and that page 335 was as far into Ulysses as Joyce's brother could get?

The auction's pièce de résistance is a jewel of Beckett studies - an exercise book containing what seems to be the text of three short prose pieces, all twined together. It's like finding the motherlode of his imagination. For Beckett fans, this unreadable mass of spidery words and crossings-out is tremendously exciting. So are the doodles in the margin - he doodled nautilus shells, flowers, even hearts reflected in water. And, at one point, I swear you can find him day-dreaming about carpets.

It's obvious. On a left-hand page, in black felt-tip pen, he's written: "Lay 7ft sq/ 9 ft sq/ 21 ft cb/27 ft cb" and beside it, he calculates the cost in a flurry of fractions. He could, of course, be working out the dimensions of the shelter in Imagination Dead Imagine. But I like to think that, just for a moment, the great Modernist was distracted from the void by thoughts of shagpile.