If you're not in the trade, they can be confusing occasions. These are some useful pointers for novice buyers

Just recently home after five days displaying our stock at the New York Antiquarian Book Fair, and I'm resting. You need to: it's a peculiarly exhausting business, exacerbated by the fact that I had flown in from Sydney via London, and kept waking at 2am longing for bacon and eggs. For the first three mornings I eventually got up at 6am and went out to dinner. Worked for me. Great steaks in New York.

We do three fairs a year – California, New York, and London – and none of them are much fun. In the olden days (I feel an old fart moment coming on) fairs had a real buzz about them. During set-up (when dealers unpack their trunks and shelve the books) other dealers would crowd round, checking out each book as it emerged, picking up the occasional bargain. Set-up was why you were there, to see if you could buy something before the public got a look-in, and sell enough in that hectic first few hours to cover your costs.

No more. Things are tighter and tougher, we've seen each other's books in catalogues and online, and there is no excitement during the two-day (too long!) set-up period. We sold one book for $5,000 (£3,000), which is better than five for $4,000, and pretty much in line with what I would have expected. The key to surviving a fair emotionally is to keep expectations realistic, which means low. I set our bottom line hope at sales of $40,000, though whether such a sum is profitable depends on what you have sold. Sometimes we have books on consignment at 20% to us, at others we may be selling something we own – better yet, have owned for ages – and get an entirely positive cashflow boost.

I need one. I have, alas, taken my eye off the ball this last year, with reading for the Man Booker International prize, and the effect on the business has been predictable. Even my bank manager is starting to twitch an eyelid. So it was essential both to get some money in from New York, and to generate a project or two with clients or other dealers: find a collection to buy, an archive to sell, a line to pursue.

But I'm getting ahead of myself, and it may be hard for you to envisage what I'm talking about. People in specialist trades often do this, and lose their audience in a welter of trade jargon and inappropriate assumption that one will be understood. So:

What is an antiquarian book fair, anyway?

It is an arena for members of the rare book trade publicly to offer their stock, and for collectors to peruse it.

That sounds a little dull, doesn't it?

OK, then. Dealers sit in their little, lit booths, displaying their wares like girls in Amsterdam windows. A few potential customers drift by. Sometimes money is exchanged. Some pleasure is had. Usually nobody gets hurt, but many wives are not told of the transaction. Or husbands.

What sort of things might one see at the fair?

Enticing ones, naturally. Hand-coloured antique maps, letters by Freud or Dickens, leatherbound sets of Jane Austen, rare books on travel, nature or military history, books illustrated by Arthur Rackham or Beatrix Potter, first editions by most of the greatest writers.

Why are first editions valuable?

They're not. Most first editions are worthless, because most books are first editions – that is, not worth reprinting. A tiny number of these first editions are desirable because they are by collected authors, and were printed in small numbers.

How can you tell if a book is a first edition?

Generally, it can be assumed unless there is any evidence to the contrary.

Why are some authors collected?

Most, because they deserve to be: John Milton, Jonathan Swift, John Keats, Charles Dickens, Mark Twain, James Joyce, Graham Greene. Some, because whatever their deserts, people love them: Agatha Christie, Ian Fleming, JK Rowling.

Does the condition of the book matter very much?

Hugely, as with all collectibles. If a book looks fresh and near-as-damn-it new, it will fetch many times more than a tired and worn copy. With 20th-century books, the presence of the original dust wrapper is crucial. A first edition of Brighton Rock (1938) without the dust wrapper is worth, say, £2,000. With it? I just paid £80,000 for one, on behalf of a customer.

Isn't that silly?

Very. But the argument is that a book without its dust wrapper is as incomplete as a Chippendale chair without its legs.

Do you think that's a fair argument?

No.

How does one know if the asking price is right?

There is no "right" price for a rare book, though there are certainly wrong ones. If you buy from a reputable member of the trade, and you are happy with your purchase, then the price is probably right enough.

But isn't a book worth whatever it fetches?

Certainly not. If I convince a muddle-headed plutocrat to pay me £1m for a common book, it doesn't mean it is worth it. It means I am a crook, and he is an idiot. Books can be under- or over-priced. That's part of the fun: trying to locate the former and avoid the latter.

When I find what I want, should I ask for a discount?

Yes.

Will I get one?

These days, for sure.

What advice could you give to a new collector?

Only buy what you like. Always buy the best copy you can afford. Buy fewer books, at a higher level. Buy from someone you have reason to trust. Spend 30% more than you can afford.

What about buying and selling at auction?

Auctioneers claim that (1) you get the best bargains if you buy at auction, and (2) you can get the best prices if you sell at auction. Both can't be true, though it is amazing how many people believe it. But about 90% of the books at auction are sold to members of the book trade. It's best to know what you are doing.

Can't you get a better deal on ebay, and cut out the middleman?

Every now and again you might. You are more likely to end up roasted with an apple in your mouth.

How do you explain the allure of rare books?

You either feel it or you don't. It's a matter of taste, and inclination, and, like love, doesn't need to be justified. I think holding a copy of the first edition of Ulysses, or Great Expectations, is thrilling, especially with a presentation inscription by the author. If you don't feel similarly, you haven't got the makings of a book collector. In fact, I don't even think I would like you.

Final note: we ended up with takings of $60,000, which was not bad, and buying three or four things at reasonable prices, that will make one or two of our collectors very happy. I am now eating breakfast in the morning, and dinner in the evening. Maybe I will sleep through the night one day soon.